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LIBRARY 

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UNIVERSITY  OF  CALIFORNIA. 


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TWENTIETH   CENTURY  TEXT-BOOKS 


EDITED    BY 

A.    F.   NIGHTINGALE,    Ph.D.,    LL.D. 

SUPERINTENDENT     OF     SCHOOLS,    COOK    COUNTY,    ILLINOIS 
FORMERLY    SUPERINTENDENT    OF    HIGH   SCHOOLS.   CHICAGO 


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ine  iiraiid  Canyon  of  tho  Colorado  icivcr. 
The  clifEs  and  terraces  above  are  carved  from  strata,  hard  and  soft.    The  depths 
the  gorge  are  in  granite.    See  page  71. 


of 


TWENTIETH   CENTURY  TEXT-BOOKS 


AN   INTRODUCTION  TO 

PHYSICAL  GEOGRAPHY 


BY 
GROVE   KARL  GILBERT 

GEOLOGIST,    UNITED    STATES    GEOLOGICAL   SURVEY 

AUTHOR    OF 

GEOLOGY    OF    HENRY    MOUNTAINS,    LAKE    BONNEVILLE,    ETC. 

AND 

ALBERT   PERRY   BRIGHAM 

PROFESSOR   OF   GEOLOGY    IN    COLGATE   UNIVERSITY 
AUTHOR    OF   TEXT-BOOK   OF    GEOLOGY 


NEW   YORK 

D.    APPLETON    AND    COMPANY 

1904 


Copyright,  1902 
By   D.    APPLETON   AND   COMPANY 


Published  June,  1902 


PEEFACE 


The  authors  have  striven  to  adapt  this  book  to  the 
earlier  stages  of  the  high-school  course.  To  this  end  the 
statements  are  simple,  technical  terms  are  sparingly  used, 
and  when  employed  they  are  promptly  defined.  Thus  ap- 
proached. Physical  Geography  may  well  serve  to  introduce 
young  students  to  the  spirit  and  method  of  science.  The 
aim  of  the  volume  as  thus  set  forth  will  explain  the  omis- 
sion of  a  few  of  the  more  difiicult  conceptions  of  land 
physiography  which  appear  in  some  school  texts. 

The  treatment,  so  far  as  possible,  is  concrete.  Wher- 
ever practicable,  each  subject  is  opened  with  a  type  case, 
in  the  description  of  which  the  terminology  is  called  forth 
and  the  principles  begin  to  appear.  Other  examples  fol- 
low, with  a  systematic  statement  of  principles,  and  the 
principles  are  further  illustrated  by  application.  This  is 
believed  to  be  in  the  line  of  good  teaching,  and  is  a  method 
to  which  our  subject  lends  itself  with  special  effectiveness. 

While  the  principles  of  Physical  Geography  belong  to 
the  earth  as  a  whole,  and  type  cases  are  cited  from  all 
regions,  the  greater  emphasis  is  put  on  our  continent.  A 
separate  chapter  on  Korth  America  would  pass  our  limit  of 
space,  but  when  the  entire  text  has  been  read,  all  the 
greater  features  of  the  continent  will  have  received 
attention. 

The  average  judgment  of  teachers  has  been  sought  in 
apportioning  the  space  to  the  several  greater  departments 
of  the  subject.  Nearly  one-half  is  given  to  the  lands.  The 
relation  of  organisms  to  the  earth  is  introduced  wherever 
appropriate,  and  the  two  closing  chapters  add  further  illus- 
trations, and  treat  the  principles  in  a  systematic  way. 


316979 


VI   AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

The  order  of  topics  has  been  adopted  after  deliberate 
consideration.  The  study  of  the  lands  is  brought  in  early, 
in  the  belief  that  here  is  the  sure  appeal  to  the  students' 
interest  and  previous  knowledge.  Alike  for  their  famili- 
arity, variety,  and  dynamic  interest,  the  stream  and  its 
valley  come  first.  This  order  is  also  conveniently  adjusted 
to  the  school  year;  field  excursions,  associated  with  the 
study  of  lands,  can  begin  in  the  autumn,  and  map  study 
and  other  laboratory  exercises  can  be  carried  on  during  the 
winter,  as  may  be  desired.  The  atmosphere  will  be  reached 
during  the  cold  season,  which,  however,  is  as  favorable  as 
any  other  for  practical  exercises  in  this  subject.  The  ocean 
is  put  late,  because  it  is  remote  from  most  schools,  and  has 
not  been  seen  by  the  majority  of  young  students.  It  is 
plain  that  shore-lines  should  follow  both  land  and  sea,  and 
that  the  formal  treatment  of  life  should  be  at  the  end. 

The  illustrations  are  closely  correlated  with  the  text, 
and  their  titles  are  accompanied  by  supplementary  expla- 
nations. Many  cross-references  are  given,  especially  where 
one  figure  shows  features  described  in  different  chapters. 

The  teachers'  pamphlet  which  accompanies  this  volume 
contains  suggestions  for  teaching  the  several  chapters,  with 
bibliography,  lists  of  practical  exercises,  arid  further  eluci- 
dation of  certain  points  in  the  text. 

Our  acknowledgments  are  due  to  Dr.  C.  Hart  Merriam, 
Chief  of  the  United  States  Biological  Survey,  who  has  read 
parts  of  the  manuscript  and  made  useful  suggestions ;  to 
Dr.  Francis  E.  Lane,  Director  of  High  Schools,  Washing- 
ton, D.  C,  who  has  read  the  proofs  and  criticized  them 
from  the  pedagogical  point  of  view ;  to  Mr.  D.  C.  Eidgley 
of  the  West  Division  High  School,  Chicago,  whose  critical 
opinion  as  to  plan  and  method  has  been  specially  valuable ; 
to  the  United  States  Geological  Survey  and  other  bureaus 
of  the  Government,  and  to  many  individuals,  who  have 
given  cordial  assistance  in  illustrating  the  volume.  Per- 
sonal acknowledgment  of  this  help  is  elsewhere  given. 

The  Authoes. 


CONTEN^TS 


CHAPTER  ^^^^ 

L— The  earth 1 

II.— The  earth  and  the  sun 17 

III.— Rivers 28 

lY. — Weathering  and  soils "^4 

V. — Wind  work 1^^ 

VI.— Glaciers .        •        .119 

VIL— Plains 1^1 

VIII.— Mountains  and  plateaus 168 

IX.— Volcanoes     .        . .196 

X. — The  atmosphere 22^ 

XL— Winds,  storms,  and  climate 253 

XII.— The  earth's  magnetism      .- 274 

XIII.— The  ocean 379 

XIV. — The  meeting  of  the  land  and  sea 302 

XV.— Life 319 

XVI. — The  earth  and  man 346 

Index 371 

vii 


LIST   OF  ILLUSTEATIOKS 


FIGURE  SUBJECT  PAGE 

Grand  Canyon  of  the  Colorado  River       .        .        Frontispiece 

1.     Curvature  of  the  ocean 2 

3.  Section  showing  soil,  waste,  and  bed-rock        ....  4 

3.  Stratified  rocks 5 

4.  Upturned  strata 6 

5.  Ideal  section  of  part  of  the  earth's  crust 7 

6.  Water  and  land  hemispheres 8 

7.  The  brook  is  a  carrier 9 

8.  Uplifted  sea-margin 10 

9.  Map  expressing  relief  by  shading .14 

10.  Map  expressing  relief  by  hachures 15 

11.  Map  expressing  relief  by  contours    ....      facing  16 
13.     Orbit  of  the  earth 19 

13.  Attitude  of  the  earth 20 

14.  Relation  of  the  earth  to  the  sun's  rays  June  31       .        .        .21 

15.  Relation  of  the  earth  to  the  sun's  rays  December  33       .        .33 

16.  Illumination  of  the  earth  in  twelve  positions  ....  24 

17.  Gorge  of  Temple  Creek,  Utah 29 

18.  Canyon  of  the  Yellowstone  River 30 

19.  A  small  river  at  low  stage 33 

30.  Ice-jam 34 

31.  Cascade  due  to  joints  and  bedding 37 

33.    Boulder  in  bed  of  Colorado  River 38 

33.  Waterfall  near  Gadsden,  Ala.  .        .        .        .        .        .        .39 

34.  Niagara  Palls 40 

35.  Section  through  Niagara  Falls 41 

36.  Alluvial  cone 43 

37.  Profiles  across  a  valley 44 

38.  Flood-plain  of  James  River,  Va 45 

39.  Scene  on  the  Mississippi  during  a  flood 46 

30.  Scene  on  the  flood-plain  of  the  Mississippi      ....  47 

ix 


X    AN  INTRODUCTION  TO  PHYSICAL  GEOGEAPHY 

FIGURE                                                                          SUBJECT  PAGE 

31.  Meanders  of  Trout  Creek,  Wyo 48 

32.  Map :  junction  of  Mississippi  and  Arkansas  rivers ...  49 

33.  A  meandering  brook 50 

34.  Map  of  Caney  Fork,  Tenn 51 

35.  Cross-profiles  of  terraces 52 

36.  Terraces  of  Uncompahgre  Valley 53 

37.  Delta  of  Chelan  Eiver 54 

38.  Map  of  the  Nile  delta 55 

39.  Section  of  a  delta 56 

40.  Miniature  delta 57 

41.  Map :  part  of  West  Virginia facing  59 

42.  Map :  head  of  Seneca  Lake,  N.  Y facing  61 

43.  Map :  delta  of  St.  Clair  River 61 

44.  Map :  part  of  Westmoreland  County,  Va.        .        .      facing  62 

45.  Delaware  Water-Gap         .        .        .        .        .        .        .        .63 

46.  Map :  trellised  drainage  in  Pennsylvania         ....  64 

47.  Map :  coastal  region,  New  Jersey  to  North  Carolina       .        .  65 

48.  Cross-profiles  of  a  divide 66 

49.  Map :  rivers  of  North  America 68 

50.  Cross-profile  of  the  Grand  Canyon  of  the  Colorado  River       .  71 

51.  Canyon  of  Snake  River 72 

52.  Watkins  Glen 75 

53.  Granite 77 

54.  Weathered  sandstone 78 

55.  Weathered  limestone .        .79 

56.  A  pebbly  rock  carved  by  rain 80 

57.  Weathered  wall  of  Trinity  College 82 

58.  Ant-hill .83 

59.  Shale  broken  by  down-hill  "  creep " 84 

60.  Avalanche  tracks 86 

61.  Granite  crags,  Black  Hills 88 

62.  Hog-back  near  Canyon,  Colo 89 

63.  Section  of  hog-back 89 

64.  Rock  ledges  and  waste  slopes 90 

65.  Mesa-butte 91 

66.  Bad  lands  in  Texas 91 

67.  Bad  lands  in  South  Dakota 92 

68.  Rounded  summits,  Appalachian  Mountains    ....  92 

69.  Mount  Sneffels,  Colo 93 

70.  Quartz  vein 97 

71.  Sink-hole  and  lake 98 

72.  Stalactites 99 


LIST  OF  ILLUSTRATIONS  xi 

FIGURE                                                                          SUBJECT  PAGE 

73.  Cleopatra  Spring  and  terrace  . 101 

74.  Old  Faithful  geyser 103 

75.  Ideal  section  of  an  artesian  well  basin 104 

76.  Artesian  well  at  Woonsocket,  S.  Dak 104 

77.  Shore  of  Lake  Michigan 106 

78.  Landslide  scenery  in  Colorado 107 

79.  Cascades  of  the  Columbia  River 108 

80.  Profile  of  a  dune 110 

81.  Diagram ;  progress  of  a  dune 110 

82.  A  patch  of  grass  on  a  field  of  loose  sand        ....  Ill 

83.  Dunes  in  a  canyon  of  Columbia  River 112 

84.  Last  house  in  Biggs,  Ore 113 

85.  Dune  on  coast  of  North  Carolina 114 

86.  Planting  grass  to  stop  drifting  of  sand 115 

87.  Sand-wear  about  boulder 116 

88.  Rock  sculptured  by  wind-driven  sand 117 

89.  Map  of  Gorner  Glacier facing  121 

90.  Gorner  Glacier         . 121 

91.  Crevasse 122 

92.  New-made  moraine 123 

93.  Glacier  of  the  Cascade  range 125 

94.  Section  of  Muir  Glacier 126 

95.  Muir  Glacier 127 

96.  College  Fiord 129 

97.  Iceberg  in  the  North  Atlantic 130 

98.  An  erratic 138 

99.  Bank  of  till 134 

100.  Shore  of  Lake  Ontario  at  Pillar  Point   .        .        .        .        .135 

101.  Kames 136 

102.  An  esker 136 

103.  Adrumlin 137 

104.  Mountain  spur  rounded  by  a  glacier 138 

105.  Tuolumne  Monument 139 

106.  Gibbs  Canyon 140 

107.  Cross-profile  of  Gibbs  Canyon         ......  140 

108.  Pot-holes 141 

109.  Shapes  of  valley  and  mountainside ;  Sierra  Nevada      .        .  142 

110.  Glacial  rock  basin 143 

111.  Map  :  United  States  in  the  Glacial  period     ....  145 

112.  Glacial  lake  in  the  Ontario  basin 147 

113.  Shore  of  ancient  lake 148 

114.  Atlantic  coastal  plain 152 


xu  AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

FIGURE  SUBJECT                                                                              PAGE 

115.  Plain  of  glacial  lake 157 

116.  Shores  of  Lake  Bonneville 158 

117.  Great  Salt  Lake  desert    .        .        .        .        .        .        .        .159 

118.  The  Great  Plains,  Colorado .        .163 

119.  The  Great  Plains,  Kansas 164 

120.  A  tundra 166 

131.     Timber-line  on  South  Lookout  Peak 169 

123.  Summit  of  Pikes  Peak 170 

133.  Map :  the  Rocky  Mountains  in  Colorado        .        .        .        .171 

124.  EstesPark -.172 

125.  Section  of  the  Rocky  Mountains 174 

126.  Bird's-eye  view  of  plateaus  in  southern  Utah         .        .        .    175 

127.  Section  of  House  range .176 

128.  Front  of  House  range ,        .        .177 

129.  Map :  Basin  ranges  and  the  Sierra  Nevada    .        o        .        .178 

130.  View  in  the  Adirondack  Mountains 180 

131.  Section  across  Appalachian  ridges 181 

132.  A  bed  of  bituminous  coal 183 

133.  Plateaus  and  valleys  about  Chattanooga        .        .        .        .184 

134.  The  Matterhorn        .        .        . 186 

135.  Placer  mining  in  North  Carolina 188 

136.  Vegetation  in  the  Rocky  Mountains 190 

137.  Furka  Pass 194 

138.  Map:  Mount  Vesuvius  and  vicinity 197 

139.  Summit  of  Mount  Vesuvius 199 

140.  Monte  Silvestri 202 

141.  The  great  crater,  Kilauea •     .    204 

142.  Profile  of  Hawaii 204 

143.  A  congealed  lava  cascade 205 

144.  Mount  Shasta 206 

145.  Mount  Hood     .        .        . 208 

146.  A  small  extinct  volcano 210 

147.  A  volcanic  crater,  holding  a  lake 211 

148.  Ideal  sections  of  a  wasting  volcanic  cone       ....    212 

149.  A  volcanic  neck 213 

150.  Palisades  of  the  Hudson 214 

151.  Obsidian  cliff   .        .        . 215 

152.  Crater  Lake 216 

153.  Mount  Mazaraa 217 

154.  Charleston  after  the  earthquake 221 

155.  Bends  in  railway  track,  made  by  an  earthquake    .        .        .    222 

156.  Density  of  the  atmosphere 226 


LIST  OF  ILLUSTRATIONS  xiii 

FIGURE                                                                          SUBJECT  PAGE 

157.  Cirrus  clouds 229 

158.  High  cumulus  clouds 229 

159.  Low  cumulus  clouds        .        .        .        .        .        .        .        .  229 

160.  Rainfall  map  of  the  United  States ....      facing  231 

161.  Rainfall  map  of  Great  Britain 234 

162.  Rainfall  map  of  Australia 235 

163.  The  thermometer 238 

164.  Absorption  of  heat  when  the  sun  is  low         ....  240 

165.  Slanting  and  vertical  sunbeams 241 

166.  Daily  curve  of  temperature 242 

167.  Relation  of  sun's  rays  to  earth  zones 243 

168.  Yearly  curves  of  temperature 244 

169.  Temperature  map  of  the  United  States,  Jan.  7, 1886,  facing  247 

170.  Isotherms  and  heat  equator  for  January        ....  248 

171.  Isotherms  and  heat  equator  for  July 249 

172.  Isotherms  and  heat  equator  for  the  year        ....  251 

173.  The  mercurial  barometer 254 

174.  Weather  map  of  the  United  States,  Jan.  7,  1886    .      facing  256 

175.  Weather  map  of  the  United  States,  Jan.  8,  1886    .      facing  256 

176.  Weather  map  of  the  United  States,  Jan.  9,  1886    .      faci7ig  256 

177.  The  anemometer 257 

178.  A  cyclonic  storm facing  258 

179.  Paths  of  cyclonic  storms 260 

180.  Winds  of  the  Atlantic  Ocean 261 

181.  Winds  of  the  Indian  Ocean  in  January  and  February  .        .  263 

182.  Winds  of  the  Indian  Ocean  in  July  and  August    .        .        .  263 

183.  A  waterspout 265 

184.  The  general  circulation  of  the  atmosphere     ....  267 

185.  Irrigation  of  a  vineyard 271 

186.  A  magnetic  needle ' .        .  274 

187.  The  compass  card 275 

188.  Magnetic  meridians facing  276 

189.  Isogonics  for  the  United  States 276 

190.  Positions  of  the  dip-needle 278 

191.  Map  :  the  western  part  of  the  Atlantic  basin         ...  280 

192.  Profile  of  the  continental  shelii 282 

193.  A  coral 283 

194.  A  coral-reef 284 

195.  Barrier  reef  and  lagoon 285 

196.  An  atoll 285 

197.  Surf 289 

198.  Low  tide 290 


xiv     AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

FIGURE                                                                          SUBJECT  PAGE 

199.  Diagram  to  illustrate  the  tides 292 

200.  Cotidal  lines  in  Delaware  Bay 293 

201.  Map :  currents  of  the  Atlantic  Ocean 295 

202.  Floe  ice 297 

203.  Sounding  apparatus 298 

204.  A  deep-sea  dredge 298 

205.  A  deep-sea  deposit 300 

206.  Map :  part  of  the  coast  of  Maine    .        .        .        .        .        .  303 

207.  Map :  Nahant  and  vicinity facing  304 

208.  Map :  New  York  and  vicinity 305 

209.  Map :  coast  of  New  Jersey 306 

210.  Map :  fiords  of  northwestern  Washington      ....  308 

211.  A  sea-cliff 310 

212.  A  barrier  and  lagoon 311 

213.  A  beach  of  gravel 312 

214.  A  curved  spit 312 

215.  Head  of  Conception  Bay 313 

216.  Map ;  the  Golden  Gate 316 

217.  Map :  estuaries  and  cities  of  England 316 

218.  Life-saving  station 317 

219.  A  broad-leaved  forest 320 

220.  A  pine  forest 321 

221.  A  tropical  forest 322 

222.  Plant  societies 325 

223.  Vegetation  of  an  arid  plain 326 

224.  A  tree-yucca 327 

225.  Musk-oxen .328 

226.  Map :  musk-ox,  moose,  and  antelope      .        .        .      facing  328 

227.  Woodland  caribous 329 

228.  Moose 329 

229.  Antelopes 330 

230.  White-tail  deer 330 

231.  Map :  caribous,  deer,  and  peccaries        .        .        .•      facing  330 

232.  Peccaries 331 

233.  A  palmetto  grove 333 

234.  A  beaver  dam 334 

235.  Cypress  knees 335 

236.  Spread  of  the  English  sparrow 338 

237.  Sea-lions 343 

238.  Crabs 344 

239.  A  wheat-field 347 

240.  Maize 348 


LIST  OF  ILLUSTRATIONS  XV 

FIGURE                                                                          SUBJECT  PAGE 

241.  A  tea-plantation 349 

242.  Bow,  arrow,  and  quiver .  350 

243.  A  cotton-field .        .351 

244.  A  stone  ax 352 

245.  A  spear-head 353 

246.  Brush  shelters 354 

247.  A  tepee 354 

248.  Oil-wells  in  California 355 

249.  A  log  cabin 356 

250.  Mountain  road  in  the  Alps 357 

251.  Pikes  Peak  railway 357 

252.  A  dug-out 358 

253.  The  modern  steamship 359 

254.  La  Santa  Maria 359 

255.  Rock-carvings  by  Indians 360 

256.  Picture-writing  by  ancient  Egyptians 360 

257.  A  Samoyed  sled 361 

258.  Indian  basketry 362 

259.  Indian  pottery . .363 

260.  A  caravan 364 

261.  The  mission  of  San  Luis  Rey 367 

262.  The  pass  of  the  Mohawk 368 

263.  New  York  harbor 369 


ACKNOWLEDGMENT  OP  ILLUSTRATIONS 

The  following  list  indicates  the  sources  of  illustrations,  or,  in  some  instances, 
the  sources  of  materials  from  which  illustrations  were  compiled.  In  a  few 
cases  the  authors  did  not  succeed  in  learning  to  whom  acknowledgment  was 
due.    Numbers  refer  to  the  Figures. 

Agassiz's  Three  Cruises  of  the  Blake,  205. 

Bartholomew  and  Herbertson's  Physical  Atlas,  161,  162,  170, 171, 172, 180, 181, 183. 

Berghaus's  Physical  Atlas,  188. 

Bureau  of  American  Ethnology,  255. 

Canadian  Geological  Survey,  211. 

Dana's  Coral  Islands,  193. 

Harrington's  About  the  Weather,  173,  177,  179,  184. 

Jordan  and  Heath's  Animal  Forms,  238. 

Jordan  and  Kellogg's  Animal  Life,  238. 

Kent's  Great  Barrier  Reef  of  Australia,  194. 

Maryland  Geological  Survey,  131. 

New  York  Central  Railroad,  262. 

New  York  State  Museum,  9. 

Nordenskiold's  Voyage  of  the  Vega,  257. 

Ober's  Storied  West  Indies,  146. 

Pennsylvania  Geoiogical  Survey,  45,  99. 

Swiss  Topographical  Map,  89. 

United  States  Coast  and  Geodetic  Survey,  10,  189, 191,  200. 

United  States  Department  of  Agriculture  :  Biological  Survey,  82,  96, 109, 197, 198, 
220,  221,  224,  226,  231,  236  ;  Bureau  of  Forestry,  219  ;  Bureau  of  Plant  Industry,  86, 
240,  245  ;  Bureau  of  Soils,  242  ;  Weather  Bureau,  157,  158,  159,  160, 169,  174,  175. 

United  States  Geological  Survey,  Frontispiece,  5,  7,  11,  18,  19,  21,  28,  29,  30,  33,  34, 
40,  41,  42,  44,  51,  52,  55,  59,  64, 66,  68,  70,  75,  79,  83,  84,  95,  100,  101,  102,  104,  108,  111,  113, 
115, 117, 120,128, 132, 133, 141, 142, 144,  147, 149,  151, 154, 155,  ia5, 206,  207.  208, 212, 213,  223, 
239.  See  also  Cross,  Darton,  Gulliver,  Holmes,  Johnson,  Russell, Walcott,  and  Willis. 

United  States  Hydrographic  Office,  201. 

United  States  Lake  Survey,  43. 

United  States  Life-Saving  Service,  218. 

United  States  National  Museum,  242,  244,  245,  256,  259. 

United  States  Surveys :  Hayden,  234 ;  Powell,  17, 126,  246, 247,  258 ;  Wheeler,  22, 87. 

H.  C.  Baker,  4  ;  H.  L.  Baldwin,  29,  30  ;  G.  H.  Barton,  103  ;  W.  Bell,  22,  87  ;  N.  W. 
Carkhuflf,  Frontispiece,  64  ;  T.  C  Chamberlin,  111  ;  J.  H.  Chapin,  110  ;  J.  H.  Clarke, 
20  ;  F.  V.  Coville,  224 ;  Whitman  Cross,  36,  69,  78,  121,  222  ;  E.  S.  Curtis,  92 ;  N.  H. 
Darton,  61,  67,  73 ;  J.  S.  Diller,  144 ;  C.  E.  Dutton,  149  ;  John  Erbach,  28 ;  A.  W. 
Greely,  202  ;  F.  P.  Gulliver,  3,  58,  118 ;  E.  K.  Hallet,  183  ;  E.  H.  Harriman,  252  ; 
Angelo  Heilprin,  260  ;  H.  W.  Henshaw,  56,  143  ;  J.  G.  Hiestand,  251  ;  R.  T.  Hill,  66, 
147  ;  J.  K.  Hillers,  17, 18, 246.  247,  258  ;  J.  A.  Holmes,  85, 114, 135,  233  ;  W.  H.  Holmes, 
26,  116,  244,  245 ;  Hook,  122 ;  J.  P.  Iddings,  151  ;  W.  H.  Jackson,  124,  234 ;  W.  D. 
Johnson,  6.5,  71,  119  ;  Cliflford  Jones,  154  ;  Arthur  Keith,  19,  68  ;  Ledrd,  140 ;  C.  H. 
Merriam.  96,  109,  220,  226,  231  ;  E.  W.  Nelson,  221  ;  H.  C.  Oberholser,  82 ;  W.  H. 
Osgood,  197  ;  T.  S.  Palmer,  236  ;  E.  A.  Preble,  198  ;  W.  H.  Rau,  150, 241,  2.53,  254,  263  ; 
J.  H.  Renshawe,  123  ;  Root,  76  ;  I.  C.  Russell,  23,  62,  77,  88, 98, 105, 106, 214.  235,  243, 249  ; 
Taunt,  .57  ;  Ernest  E.  Thompson,  227,  228,  229.  230  ;  H.  W.  Turner,  108  ;  A.  C.  Vro- 
man,  261  ;  C.  D.  Walcott,  31,  54,  97,  215  ;  Leo  Wehrli,  134,  254 ;  T.  C.  Weston,  211 ; 
Bailey  Willis,  37,  60,  93,  136. 

The  relief  maps  represented  in  Figs.  9,  111,  129,  133,  208,  were  modeled  by 
Edwin  E.  Howell, 
xvi 


AN    INTRODUCTION 
TO    PHYSICAL    GEOGRAPHY 


CHAPTEE  I 


THE   EARTH 


1.  Form  of  the  earth. — On  September  6,  1522,  a  little 
company  of  weather-beaten  and  weary  sailors  brought  their 
vessel  to  rest  in  a  Spanish  port.  Three  years  before,  Ma- 
gellan had  led  them  forth,  with  a  fl^et  of  five  ships,  to  find 
the  Spice  Islands  by  a  western  route.  Through  romantic 
adventure  and  heroic  endurance  the  commander  brought 
his  expedition  around  the  Horn  and  across  the  Pacific  to 
the  Philippine  Islands,  where  he  was  slain.  Eighteen  men 
fought  their  way  about  the  Cape  of  Good  Hope  and  saw 
their  homes  again.  Xo  one  before  them  had  sailed  around 
the  world.  They  showed  by  experiment  that  the  earth 
could  be  circumnavigated.  We  sometimes  say  that  they 
proved  it  to  be  round.  This  is  not  strictly  true.  It  might 
have  had  the  shape  of  an  egg^  or  have  been  in  some  other 
way  very  different  from  a  sphere.  The  voyage  did  prove, 
however,  that  our  earth  lies  free  in  space  and  is  bounded  by 
curved  surfaces. 

Columbus  and  other  modern  men  were  not  the  first  to 
infer  that  the  earth  is  round.  Some  ancient  philosophers 
felt  quite  sure  of  it,  for  they  noted  that  different  groups  of 
stars  were  seen  from  places  far  north  or  south,  and  on  a  flat 
earth  this  would  not  be  so.  But  full  proof  came  with  all 
the  freshness   of   first  discovery  to  modern  peoples,  who 

1 


AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


found  even  more  complete  evidence  than  is  afforded  by  a 
voyage  around  the  world.  The  sailor  approaching  port 
sees  land  from  the  mast  before  he  sees  it  from  the  deck, 

and  he  discerns  the 
spires  and  roofs  be- 
fore the  foundations 
come  to  view.  The 
outgoing  ship  is  soon 
"  hull  down "  on 
the  horizon,  and  at 
length  the  masthead 
disappears.  The  sur- 
face of  a  lake  four 
miles  wide  is  curved 
enough  to  conceal 
"  ^     '"  the  lower  five  feet  of 

Fig.  l.-The  curvature  of  the  ocean.    The  water  partly    ^n  objCCt  BCCn  acrOSS 
conceals  the  distant  ships.  '' 

its  surface.  The 
earth  casts  a  curved  shadow  on  the  moon  when  it  comes 
between  it  and  the  sun. 

Thus  we  know  that  the  earth  is  nearly  round.  It  is 
flattened  about  13  miles  at  each  pole,  and  there  are  other 
small  irregularities;  so  that  if  it  were  halved  along  any 
plane,  the  cut  surface  would  not  be  a  perfect  circle.  The 
earth  is  not  a  perfectly  rigid  body,  but  may  change  its 
shape  from  age  to  age,  like  a  rubber  ball  compressed  in 
slight  degree,  now  at  one  point  and  now  at  another.  It 
has  been  the  work  of  the  last  two  centuries  to  find  these 
small  departures  from  the  pattern  of  a  sphere. 

2.  Latitude  and  longitude. — It  is  an  important  work  of 
every  great  nation  to  sound  and  chart  the  seas.  If  the  sea  is 
to  be  a  highway,  its  shoals  and  channels,  harbors  and  islands 
must  be  known  in  ways  that  all  can  understand.  Even 
the  wastes  of  mid-ocean  must  be  so  mapped  that  the  mari- 
ner can  tell  where  he  is  and  whither  he  is  going.  When  a 
new  shoal  is  found  by  any  sailor,  it  should  be  made  known 


THE  EARTH  3 

to  every  shipmaster  sailing  in  those  waters.  It  would  be 
described  exactly  and  in  the  shortest  terms  by  referring  it 
to  imaginary  lines  of  latitude  and  longitude.  Physical 
geographers  deal  most  with  actual  things  seen  on  the  earth, 
but,  like  students  of  political  or  commercial  geography, 
they  fall  back  upon  this  ingenious  plan  for  indicating,  in 
maps  and  in  written  speech,  the  exact  positions  of  geo- 
graphic features. 

We  start  with  the  poles,  as  marking  the  line  about 
which  the  earth  turns.  The  circle  midway  between  the 
poles,  dividing  the  surface  into  halves,  we  agree  to  call  the 
equator.  We  then  imagine  circles  parallel  to  this,  a  degree 
apart  and  growing  smaller  in  size,  all  the  way  to  either 
pole.  We  call  these  parallels  of  north  or  south  lati- 
tude, and  number  each  way  from  equator  to  pole.  By 
their  aid  any  point  on  the  earth  can  be  described  as  to  its 
distance  from  the  middle  or  equatorial  line,  and  the  dis- 
tance can  be  plotted  on  a  globe.  When  this  method  is 
used,  distances  are  indicated  in  degrees,  minutes,  and  sec- 
onds. A  degree  of  latitude  covers  about  69  miles.  It  is  a 
trifle  longer  near  the  poles  than  near  the  equator,  because 
there  the  curve  of  the  surface  is  less. 

We  also  imagine  a  system  of  lines  cutting  the  parallels 
at  right  angles  and  meeting  in  the  poles.  Each  is  a  half- 
circumference  of  the  earth,  and  we  think  of  them  as  one 
degree  apart  around  the  earth.  We  call  them  meridians, 
because  it  is  noon  at  the  same  time  at  all  points  of  any  one 
of  them.  A  degree  of  longitude  covers  about  69  miles  at 
the  equator,  but  diminishes  to  zero  at  either  pole.  It  is 
purely  a  matter  of  choice  where  we  begin  to  reckon,  but  it 
is  common  the  world  over  to  call  the  meridian  passing 
through  the  Greenwich  Observatory,  near  London,  zero,  and 
number  west  or  east  to  180°.  Thus  all  points  in  ^N^orth  Amer- 
ica are  in  west  longitude  and  in  north  latitude.  The  posi- 
tion of  the  Capitol  at  Washington  is  38°  63'  23''.2  N^.  lat., 
77°  00'  33".5  W.  long. 


4    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

This  scheme  of  lines  is  particularly  useful  in  mapping 
and  navigating  the  sea,  and  in  making  large  surveys  on  the 
land,  as  for  government  or  State  boundaries.  It  enables  us 
to  indicate  the  relations  of  two  distant  points  more  exactly 
than  by  referring  them  to  neighboring  rivers,  lakes,  or 
mountains,  though  the  latter  way  is  often  more  instructive. 

3.  The  earth  without  and  within. — Xo  one  knows  much 
about  the  inside  of  our  globe.  Yet  most  of  its  bulk  and 
weight  are  far  within  the  surface,  and  geography,  which 
looks  at  the  earth  as  a  whole,  must  take  notice  of  it.  The 
interior  is  believed  to  be  very  hot.  It  is  known  that  for 
every  50  feet  of  descent  into  a  deep  mine  there  is  a  gain  of 
about  one  degree  in  temperature ;  and  the  lavas  of  volca- 
noes, flowing  up  from  sources  miles  below  the  surface,  are 
as  hot  as  molten  iron  or  copper. 

It  is  also  known  that  the  earth  is  about  twice  as  heavy  as 
the  same  bulk  of  the  common  surface  rocks  would  be.  This 
may  mean  that  the  inside  is  made  largely  of  iron  and  other 
metals.  Or  it  may  mean  that  the  materials  are  like  those 
of  the  surface,  but  are  so  packed  and  condensed  under 
pressure  as  to  weigh  much  more  for  the  same  bulk. 

The  outer  part  of  the  earth,  like  the  outside  of  a  loaf  of 
bread,  is  called  the  Crust.     We  know  that  the  crust  is  cold 

and  rigid,  and  that  the  in- 
terior is  hot.  It  was  for- 
merly believed  that  the 
whole  interior  is  molten, 
but  that  view  is  now  ques- 
tioned. We  use  the  word 
Fig.  2. -Ideal  cutting,  or  "section,"  ehow-  -v^ithout  implying  a  theory 

ing  soil  (8),  the  mantle  of  waste  {w).  and  '^ /      j  *' 

bed-rock  (r).  as  to  the  State  of  the  inte- 

rior, or  even  that  there  is 
some  level  of  abrupt  passage  from  the  rind  to  the  core  of 
the  earth.  Crust  is  a  convenient  word  for  that  outer  part 
with  which  geography  has  most  to  do.  In  it  are  useful 
minerals.     Its  decay  forms  soil.     Over  it  are  the  waters 


THE  EARTH  5 

and  the  atmosphere.     On  or  near  its  surface  are  the  hosts 
of  living  things.     It  is  the  chief  subject  of  our  study. 

4.  The  rocks  of  the   earth's  crust.— Nearly  everywhere 
there  is  a  blanket  of  soil  and  stony  waste.     On  the  very 


Fig.  3.— Stratified  rocks  seen  in  the  bank  of  a  creek.    Layers  of 
arated  by  layers  of  soft  shale. 


imestone  are  sep- 


surface  is  commonly  a  true  soil,  in  which  plants  will  grow. 
Below  is  clay,  or  sand,  or  loam,  or  gravel.  Under  this  loose 
layer,  and  rising  out  of  it  in  mountains  and  ledges,  is  the 
hard  "  bed-rock,"  which  continues  to  great  depths,  or  until 
we  come  to  the  unknown  conditions  of  the  earth's  interior. 

We  must  now  take  these  thick  rocks  and  divide  them 
into  two  great  sorts.  This  is  not  a  complete  division,  for 
the  geologist  would  find  many  kinds,  but  the  student  of 
physical  geography  will  find  it  most  useful  to  know  the  two 
classes. 

In  large  parts  of  the  continents  the  rocks  are  in  layers 


6         AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


and  horizontal.  The  student  will  remember  quarries  in 
which  the  layers,  each  a  few  inches  or  a  foot  or  two  thick, 
lie  tier  on  tier.  Some  are  harder  and  some  are  softer,  and 
they  may  be  of  many  colors,  but  they  are  either  sandstones, 

shales,  or  limestones 
(sections  64-66).  They 
were  originally  formed 
as  layers  of  mud  or 
sand  in  lakes  or  seas, 
and  have  since  been 
hardened  into  rock.  In 
other  places  the  same 
rocks  are  found  in  the 
same  sort  of  layers,  but 
the  layers  are  tipped  to 
various  slopes,  or  even 
stand  on  edge.  Rocks 
in  layers  are  called 
Stratified  rocks. 

In  other  regions  the 
surface  rocks  are  not  in 
layers,  and  are  neither 
sandstone,  shale,  nor 
limestone,  and  are  crystalline.  They  have  come  to  be  what 
they  are  in  ways  too  difficult  and  various  to  be  explained 
here.  Many  of  them  have  cooled  from  a  melted  or  much- 
heated  state;  and  they  are  called  Igneous  or  Crystalline 
rocks.  Granite  (section  67)  may  be  taken  as  the  most 
familiar  illustration  of  the  class.  They  are  more  likely 
to  appear  at  the  surface  in  mountain  regions,  but  they 
exist  everywhere  at  some  distance  underground.  If  we 
were  to  dig  or  bore  deep  enough  in  the  layered  or  strati- 
fied rock,  we  should  always  find  the  other  kind  at  the 
bottom.  The  igneous  rocks,  therefore,  make  up  the  larger 
part  of  the  crust,  but  over  them  in  vast  regions  the  beds 
of  stratified  rock  lie  as  a  cover. 


Fig.  4.— Limestone  strata  which  have  been  up- 
turned in  a  mountain. 


THE  EARTH  T 

If  we  could  pierce  the  crust  under  the  sea  we  should 
find  first  the  soft  muds,  then  perhaps  hard  muds  or  strati- 
fied rocks,  and  still  below  the  hard  foundation  of  older 
rocks. 


Pig.  5.— Ideal  section  of  part  of  the  earth's  crust,  with  landscape  above.  Granite  and 
other  crystalline  rocks  appear  with  irregular  outlines  at  the  bottom  of  the  section; 
over  them  are  stratified  rocks,  partly  bent  and  partly  flat.  The  forms  of  the  land- 
scape are  related  to  the  arrangement  of  the  rocks. 


5.  Land  and  water. — The  student  already  knows  the  rel- 
ative areas  of  water  and  land,  and  knows  also  much  of  the 
continents  and  their  arrangement.  It  is  almost  certain 
that  there  is  open  sea,  save  for  ice,  about  the  north  pole, 
and  land  sheeted  with  ice  about  the  south  pole.  The 
great  lands  are  wide  at  the  north,  where  they  almost  en- 
circle the  world.  The  great  seas  are  continuous  toward 
the  south,  and  reach  northward  in  the  several  oceans.  We 
may  regard  the  seas  as  one  spherical  sheet  of  water,  inter- 
rupted by  lands  large  and  small.  The  great  lands  narrow, 
or  are  invaded  by  extensions  of  the  sea,  near  the  equatorial 
belt,  so  that  the  cutting  of  slender  necks  at  Suez  and  in 
Central  America  completes  a  water  passage  around  the 
globe.  Low  coral  islands  and  high  volcanic  islands  are 
numerous  in  the  seas,  and  there  is  no  point  on  the  globe 
which  is  more  than  a  few  hundred  miles  from  some  land. 
We  can  also  make  an  instructive  division  of  the  earth  into 


8    AN  INTRODUCTION  TO  PHYSICAL  aEOGRAPHY 


a  land  hemisphere,  having  its  center  in  western  Europe, 
and  a  water  hemisphere  with  its  center  near  Xew  Zealand. 
These  facts  will  help  us  toward  imagining  the  earth's 
surface  as  a  whole,  but  it  is  much  more  important  to  know 
how  the  sea  and  land  affect  each  other.  The  mud  which 
stains  the  waters  of  the  brook  after  a  heavy  shower  will  go 
to  the  river  and  then  to  the  sea,  and  in  its  bottom,  some  of 
it  hundreds  of  miles  from  shore,  will  come  to  rest.  Thus 
the  material  of  the  land  is  constantly  cast  into  the  sea. 
The  sun  beats  on  the  surface  of  the  sea  and  lifts  its  waters 
as  invisible  vapor.  This  is  blown  over  the  land,  condensed 
to  rain  or  snow,  and  falls,  creating  all  rivers,  watering  the 
fields,  and  making  life  on  land  possible.  So  far  as  we  can 
see,  a  living  world  without  the  ocean  is  impossible.  In  the 
chapters  on  the  land  and  the  ocean  we  shall  learn  of  many 


Fig.  6. 


Water  hemisphere. 


Land  hemisphere. 


other  links  that  bind  the  two,  and  make  our  planet  one 
world  indeed.  There  is  no  part  of  it  so  distant  that  it  does 
not  help  to  make  us  what  we  are. 

If  we  study  the  brook  more  closely  we  find  that  every 
time  a  flood  courses  through  it  its  channel  is  changed.  Here 
an  overhanging  bank  is  washed  away,  making  a  tree  fall ; 
there  a  shelving  shore  is  built  higher  by  a  deposit  of  mud 
or  sand.  Here  a  gravelly  bar  grows  longer  or  shorter; 
there    a    swimming-pool    is    made    deeper    or    shallower. 


THE  EARTH 


9 


Through  such  changes  we  come  to  know  that  the  brook  is 
a  carrier  not  only  of  fine  mud,  but  of  sand  and  gravel, 
catching  them  as  they  fall  from  bank  or  cliff,  and  driving 
and  rolling  them  onward  to  the  river  and  the  sea. 


Fig.  7.— The  brook  is  a  carrier.  As  the  rock  of  the  high  bank  crumbles,  fragments 
fall  into  the  water  and  are  swept  away.  The  brook  is  also  a  digger.  In  time  of 
flood  its  strong  current,  thrown  against  the  bank  at  the  bend,  tears  out  stones 
and  earth. 


6.  The  outflow  of  lava  in  volcanoes. — Not  less  strange 
and  wonderful  to  us  is  the  flow  of  lava,  pouring  out  of  the 
earth  like  molten  iron  from  a  furnace,  hardening  as  it  cools, 
and  pouring  and  hardening  again  and  again,  till  a  hill  or 
mountain  is  built  up ;  or  the  bursting  of  other  lava  into 
ash-like  fragments  which  rain  on  the  surrounding  lands 
till  fields  and  meadows,  and  even  forests  and  cities,  are 
buried  and  destroyed.  The  volcano  tells  not  only  of  great 
heat  below  the  outer  layers  of  the  crust,  but  of  forces  so 


10      AN   INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

enormous  that  the  crust  itself  is  rent  in  giving  passage  to 
the  pent-up  liquid. 

7.  Rivers  of  ice,  or  glaciers. — Among  the  peaks  of  lofty- 
mountains  are  other  streams  made  of  ice,  not  more  marvel- 
ous, perhaps,  than  streams  of  water,  but  exciting  our  wonder 
because  far  away  and  unfamiliar.  Glaciers  are  fed  by  the 
wintry  snows  of  the  cold  heights,  and  creep  downward  until 
melted  by  the  warmer  air  of  the  lowlands.  They  also  are 
carriers,  plucking  pebbles  and  boulders  and  fine  earth  from 
their  channels,  and  dropping  them  in  the  valleys  below. 
Many  centuries  ago,  before  the  records  of  history  began, 
immense  glaciers,  or  ice-sheets,  overspread  mucli  of  Canada 
and  encroached  on  the  United  States  from  the  north.  The 
period  of  this  ice  invasion  is  called  the  Ice  Age,  or  the 
Glacial  Epoch,  and  the  geography  of  many  lands  then 
underwent  important  changes. 

8.  Up  and  down  movements  of  the  land. — Many  students 
will  find  near  their  homes  stratified  rocks  which  contain 
shells  that  grew  in  the  sea.  They  were  enclosed  in  muds 
of  the  sea-bottom,  the  muds  were  hardened  into  the  rocks 
we  see,  and  rocks  and  shells  are  now  perhaps  hundreds  of 


Fig.  8.— An  aplifted  sea-margin.  The  beating  of  waves  washes  away  rock  and  earth 
at  the  shore,  especially  on  bold  capes,  making  cliffs  and  shelves.  When  the  land 
is  lifted  higher  the  same  thing  is  done  along  the  new  shore-line. 

feet  above  the  water.  This  means  that  old  sea-bottoms  have 
come  up  out  of  the  water  and  now  form  land.  Can  we  find 
any  lands  which  are  now  experiencing  such  uplift,  or  which 


THE  EARTH  11 

have  thus  risen  in  recent  times  ?  On  the  south  shore  of 
Maine  geologists  have  found  old  sea-beaches  more  than  200 
feet  above  the  sea.  These  tell  that  that  region  has  risen 
up  out  of  the  ocean  late  in  the  making  of  our  continent. 
Similar  old  sea-margins,  cut  against  the  slopes  of  the  land- 
are  found  on  the  borders  of  Alaska  and  Scotland  and  Kor- 
way.  Villages  and  landing-places  have  seen  the  sea  flow 
away  from  them  since  men  began  to  record  modern  history. 
In  other  places  sinking  has  been  going  on.  Such  move- 
ments go  on  very  slowly — so  slowly  that  they  can  not  be 
felt  or  seen.  Only  the  result  can  be  measured  after  a 
period  of  time. 

9.  Continuous  change. — It  is  important  to  obtain  a  clear 
understanding  of  the  fact  that  the  face  of  the  earth  is  al- 
ways changing.  The  mud  and  sand  of  the  flooded  brook 
were  washed  by  rain  from  field  and  hillside,  and  their 
removal  changed  the  form  of  the  surface.  When  their 
journey  ends  and  they  again  come  to  rest  under  the  sea, 
they  change  the  form  of  the  sea-bottom.  The  work  of  each 
storm  may  be  so  small  that  we  can  hardly  detect  it ;  but 
time  is  long,  and  all  the  storms  of  thousands  of  centuries 
can  even  remove  hills,  or  hollow  out  valleys,  or  make  shoals 
where  once  the  ocean  was  deep.  A  glacier  creeps  along  so 
slowly  that  we  must  make  careful  measurement  to  be  sure 
that  it  moves  at  all,  but  by  grinding  away  for  ages  it  makes 
great  changes  in  the  form  of  its  bed  and  builds  high  hills 
of  stony  waste  at  its  end.  The  work  of  the  volcano  is  more 
conspicuous,  because  it  heaps  up  a  hill  or  blasts  out  a  hol- 
low by  a  single  effort.  Where  the  land  is  rising,  bays  are 
becoming  gradually  shoal  and  narrow,  capes  are  extending 
and  islands  are  broadening,  straits  are  giving  place  to 
isthmuses,  and  the  whole  coast  is  gaining  new  outlines. 

We  must  understand,  too,  that  such  changes  have  been 
in  progress  for  an  immense  period  in  the  past.  By  means 
of  them  the  forms  of  land  and  sea,  the  plains  and  valleys, 
hills  and  mountains,  have  been  made  and  remade,  until 


12       AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

every  feature  is  the  result  of  change.  There  was  a  time 
when  men  thought  of  the  earth  as  unchanging,  but  the 
geographer  no  longer  speaks  of  the  "  everlasting  hills."  He 
believes  each  shape  of  the  surface  to  have  been  produced 
through  some  series  of  changes,  and  in  seeking  to  learn  the 
history  of  its  origin  finds  never-failing  interest.  A  growing 
world  is  a  living  world,  and  to  study  geography  well  is  to 
look  upon  the  noblest  of  panoramas. 

10.  The  atmosphere. — Here  is  land  and  there  is  sea,  but 
over  all  is  the  air,  invisible,  but  keenly  felt,  forming  a 
blanket  covering  the  continents  and  the  oceans.  It  is  in- 
deed a  blanket,  for  without  its  protection  heat  would  fly  off 
into  space  and  the  surface  of  the  earth  would  be  always 
frozen.  It  is  never  long  still,  and  in  its  ebb  and  flow,  its 
creep  and  rush  over  the  earth,  .it  is  the  great  carrier  of 
clouds  and  of  heat.  It  is  in  some  way  breathed  by  all  living 
creatures,  even  by  the  lowest  plants  and  by  animals  in  the 
deepest  seas,  and  thus  in  many  ways  is  necessary  to  life. 
We  shall  come  to  its  study  in  later  chapters,  and  find  it  one 
of  the  most  important  themes  in  increasing  our  knowledge 
of  the  earth. 

11.  Living  things. — The  early  settlers  found  New  Eng- 
land and  the  Appalachian  region  covered  with  dense  for- 
ests. Through  the  Mississippi  valley  grew  the  grasses  and 
flowers  of  the  prairies  and  the  endless  woods  of  the  region 
toward  the  Gulf.  In  the  western  plains  and  valleys  are 
grasses  for  pasturage,  and  wide  tracts  of  bushes  and  herbs. 
In  the  western  mountains  trees  and  meadows  and  gardens 
of  Alpine  flowers  predominate  over  rocks  and  snows.  And 
so,  the  world  over,  the  carpet  of  vegetation  colors  every 
picture.  Insects  and  birds  fill  the  lower  air,  beasts  tread 
the  ground,  and  worms  and  burrowing  creatures  occupy 
the  soil.  All  lakes  of  fresh  water  teem  with  fish,  and 
the  ocean  has  infinitely  more  life  than  all  the  lands 
together.  We  do  not,  of  course,  forget  that  land  life  is 
much  of  it  of  a  higher  sort;  but  we  find  the  best  teach- 


THE  EARTH  13 

ing  of  geography  in  seeing  how  the  land  and  sea,  and  the 
sea  of  air  above  them,  have  helped  to  make  all  living  crea- 
tures what  they  are.  An  oyster  can  not  live  upon  the  land 
nor  an  oak  in  the  sea.  A  palm  would  die  in  Greenland, 
and  a  reindeer  would  pine  in  a  southern  home.  Each  has 
come  to  its  estate  through  the  long  history  of  its  ancestors, 
living  in  conditions  of  moisture  or  dryness,  heat  or  cold, 
and  influenced  by  them. 

12.  Geography. — If  we  wish  to  know  the  other  planets 
in  our  solar  system,  or  the  arrangement  of  the  fixed  stars, 
we  study  astronomy.  If  we  would  learn  the  laws  and  uses 
of  electricity,  we  turn  to  physics.  If  we  desire  knowl- 
edge of  the  ancient  history  of  our  earth,  of  the  growth 
of  its  lands  and  of  the  animals  and  plants  of  long  ago,  we 
study  geology.  Should  our  object  be  to  understand  animals 
or  plants  in  a  thorough  way,  zoology  or  botany  would  be 
our  theme.  But  our  purpose  is  to  know  the  earth  as  a 
whole.  Land  and  sea,  air  and  rock,  beast  and  tree  combine 
to  form  it ;  and  we  give  some  study  to  each,  not  to  know 
all  about  any  one,  but  to  see  how  each  controls  the  rest, 
and  how  all  work  together.  This  is  the  science  of  geog- 
raphy. And  because  we  deal  with  the  natural  earth  and 
not  with  its  political  provinces,  we  call  our  subject  Physical 
Geography. 

The  earth  belongs  to  the  sun  and  revolves  around  it. 
Thus  we  must  touch  upon  astronomy.  The  winds  and 
storms  and  tides  and  flowing  waters  show  the  working  of 
forces,  and  so  we  look  to  physics  for  help.  Some  animals 
have  become  used  to  cold  climates,  others  are  fitted  to  en- 
dure heat.  Some  plants,  like  the  dandelion,  are  widely 
scattered,  because  the  seeds  have  become  fitted  for  travel 
by  the  winds.  Some  live  on  high  mountains,  some  in 
swamps,  and  others  in  deserts.  The  zoologist  and  botanist 
will  tell  us  about  these,  and  with  their  help  we  shall  see  the 
earth  as  the  home  of  life.  To  form  true  notions  of  our 
whole  planet,  because  men  live  upon  it  and  because  they 


14      AN  INTRODrCTlON  TO  PHYSICAL  GEOGRAPHY 

have  been  much  influenced  by  their  surroundings— this  is 
the  purpose  of  geography. 

13.  Maps. — These  are  a  convenient  means  of  bringing 
the  earth  under  our  eye  and  of  describing  it  to  others. 
They  are  miniature  representations  of  the  whole  earth,  or 
of  a  part  of  it.     In  a  small-scale  map  one  inch  might  repre- 


FiG.  9.— Map  expressing  relief  by  shading.  From  a  model  of  the  district  a  photo- 
graph was  made,  and  this  was  copied  by  the  "half-tone"  process.  Scale,  one 
inch  equals  five  miles.  The  map  shows  parts  of  the  Hudson  Valley  and  the 
Catskill  Mountains,  or  Plateau.    See  pages  66, 161,  and  182. 


sent  hundreds  of  miles,  as  in  a  common  page  map  of  North 
America.  But  on  the  atlas  sheets  published  by  the  United 
States  Geological  Survey  one  inch  commonly  represents 
one  mile.  In  such  a  map  many  natural  and  artificial  fea- 
tures can  be  included.  The  map  scale  for  a  closely  popu- 
lated city  would  be  much  greater  than  this.  Upon  consult- 
ing a  map  the  scale  should  be  at  once  sought. 

Various  devices  are  used  to  show  not  merely  the  ground- 


THE   EARTH 


/T' 


15 


plan  or  arrangement,  but  reliefs  or  elevations  as  well.  This 
may  be  done  by  shading  (Fig.  9),  or  by  short  lines  called 
Hachures  (Fig.  10),  or  by  curved  lines  known  as  Contours 
(Fig.  11).  Hachures  are  short  lines  pointing  in  the  direc- 
tion of  the  slope  of  the  ground.  They  are  made  heavier 
where  the  slope  is  steeper.     A  contour  is  everywhere  at 


Fig.  10.— Map  expressing  relief  by  hachures.     Shows  part  of  Cape  Cod,  Mass.    Scale, 
one  inch  equals  two-thirds  of  a  mile. 


right  angles  to  the  direction  of  slope.  It  represents  the 
course  one  might  take  if  he  walked  horizontally  across 
sloping  ground,  choosing  his  way  so  as  to  go  neither  up  nor 
down.  The  outline  of  a  lake  is  a  contour  about  the  valley 
in  which  the  lake  lies.  If  water  should  be  added  to  the 
lake  until   it    is   ten    feet    deeper   the   new  lake   outline 


16       AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

would  be  a  contour  at  a  level  ten  feet  higher.  The  con- 
tours of  a  map  represent  level  lines  about  the  sides  of 
valleys  and  hills,  each  at  a  height  differing  by  a  regular 
interval  from  that  of  the  contour  next  below  it.  In  Fig.  11 
the  contour  interval  is  ten  feet,  in  Fig.  42,  twenty  feet. 
If  the  contours  are  crowded,  the  slope  is  steep.  If  they 
are  far  apart,  the  ground  is  nearly  level. 

Models  are  relief  maps,  and  are  thus  more  true  to  nature, 
if  well  made,  than  flat  maps.  Many  models  are  deceptive 
and  harmful  because  the  heights  and  slopes  are  so  exagger- 
ated as  to  teach  untruth ;  but  there  are  also  many  truthful 
models,  especially  of  small  regions,  in  which  the  scale  for 
heights  is  the  same  as  the  scale  for  distances.  A  globe  is 
the  most  general  map,  and  it  may  be  smooth,  or  wrought  in 
relief.  Pictures  are  of  use  in  geography.  They  show 
smaller  areas,  but  in  greater  detail.  Specimens  are  in  some 
ways  best,  for  they  are  actual  parts  or  products  of  the  earth. 
We  illuminate  maps,  models,  pictures,  and  specimens  by 
records  of  travel,  and,  best  of  all,  travel  ourselves,  and  thus 
make  geography  interesting  and  real. 


Fig.  11.— Map  expressing  relief  by  contours.  Contours  are  in  brown,  water  features 
in  blue.  Contour  interval,  ten  feet.  Figures  show  the  heights  of  contours  above 
sea-level.  Contours  at  450,  500,  550,  600,  and  650  feet  above  sea-level  are  distin- 
guished by  heavier  lines.  Scale,  one  inch  to  the  mile.  The  area  represented  is  in 
the  State  of  Illinois.    See  pages  15  and  67. 


CHAPTER  II 

THE  EARTH  AND  THE  SUN 

14.  The  sun. — The  earth  may  be  said  to  belong  to  the 
sun.  To  no  other  heavenly  body  are  we  related  in  any  such 
close  way.  We  travel  around  it,  we  can  not  get  away  from 
it,  and  without  it  there  could  be  no  life  on  the  earth.  We 
can  not  comprehend  what  astronomers  tell  us  of  its  size. 
It  means  little  to  say  that  its  diameter  is  nearly  a  million 
miles.  But  it  helps  our  imagination  more  to  say  that  it  is 
nearly  four  times  as  far  through  the  sun  as  it  is  from  here 
to  the  moon.  Large  as  our  planet  seems  to  us  when  we 
travel  to  distant  lands,  it  is  a  mere  speck  in  comparison 
with  the  sun.  If  the  setting  sun,  seen  through  a  hazy 
atmosphere,  seems  to  us  as  big  as  a  cart-wheel,  we  must  use 
our  reason  to  try  to  appreciate  its  real  size.  We  can  better 
understand  that  it  is  very  hot.  Its  outer  gases,  rising  and 
sinking  in  mountains  and  gulfs  of  flame,  but  faintly  inform 
us  as  to  the  inconceivable  heat  of  the  seething  fluids  within. 
One  might  freeze  within  a  half-mile  of  the  greatest  confla- 
gration kindled  by  man  ;  but  we  often  screen  ourselves  from 
the  sun's  rays  at  a  distance  of  almost  a  hundred  million 
miles. 

15.  The  earth  is  one  of  the  planets. — A  family  of  globes 
belongs  to  the  sun,  making  up  the  solar  system.  Here 
belong  Mercury  and  Venus,  nearer  the  sun  than  we  are,  and 
Mars,  Jupiter,  Saturn,  Uranus,  and  Neptune,  whose  paths 
are  outside  of  ours.  Satellites  like  our  moon,  and  many 
small  bodies  called  asteroids,  are  in  the  sun's  family,  but 
the  study  of  these  belongs  chiefly  to  astronomy.     Our  aver- 

17 


18      AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

age  distance  from  the  sun  is  nearly  93,000,000  miles.  The 
distance  changes  somewhat  in  different  parts  of  the  year, 
and  in  different  periods  of  time.  We  shall  understand  our 
own  planet  better  if  we  remember  that  all  the  others  like- 
wise have  a  turning  motion,  like  a  top,  and  all  follow  paths 
around  the  central  sun. 

16.  The  sun  warms  and  lights  the  earth. — It  is  hardly  too 
much  to  say  that  the  warming  of  the  earth  by  the  sun  is 
more  important  than  all  other  facts  of  geography  taken 
together.  Without  this  supply  of  heat  the  oceans  would 
become  ice,  and  all  lands  would  be  frost-bound,  save  where 
volcanoes  are  at  work.  There  could  be  no  life  on  the  earth, 
no  clouds,  rain,  or  snow.  Without  rivers  or  glaciers,  without 
variation  of  temperature,  and  without  life,  no  changes  could 
come  over  the  forms  of  the  land.  Here  would  be  a  dark 
world  also.  With  no  sun,  no  reflected  light  from  the  moon, 
and  no  clouds,  perpetual  night  would  be  relieved  only  by 
the  faint  light  of  the  fixed  stars.  Even  on  a  warm  earth 
no  life  of  high  order  could  exist  without  light.  So  depend- 
ent are  we  on  the  sun  that  we  might  almost  say  that  our 
whole  study  of  Physical  Geography  is  a  search  for  the  conse- 
quences that  flow  from  our  relation  to  the  sun. 

17.  The  earth  turns  around  at  a  uniform  rate. — The  time 
for  a  complete  turn  we  call  a  day,  and  for  convenience  we 
divide  it  into  twenty-four  parts  and  call  them  hours.  The 
turning  is  always  about  one  line,  as  with  a  top,  and  we  im- 
agine such  a  line  passing  through  the  center  of  the  earth 
and  call  it  the  Axis.  The  points  where  this  line  reaches 
the  surface  we  call  the  north  and  the  south  poles.  The 
spinning  motion  of  the  earth  is  commonly  known  as  its 
Rotation.  A  top  always  runs  down.  The  earth  turns  with 
but  slight  loss  of  speed  from  age  to  age.  The  rubbing  or 
friction  of  the  top  against  the  floor  and  against  the  atmos- 
phere brings  it  to  rest.  The  earth  (of  which  the  air  is 
only  a  part)  requires  no  mechanical  support,  and  swings 
free  in    relatively  empty  space.      The  friction   is  almost 


THE  EARTH  AND  THE  SUN 


19 


nothing,  and  it  goes  on  with  the  impulse  given  to  it  at  its 
beginning. 

18.  The  turning  earth  swings  around  the  sun. — The  time 
for  a  complete  swing  we  call  a  year.  While  the  earth  is 
making  one  swing,  each  part  of  it  is  turned  toward  the 
sun  about  365  times ;  hence 
we  say  that  a  year  is  made 
up  of  so  many  days.  From 
earliest  ages  men  have  thus 
marked  the  greater  and 
lesser  divisions  of  time. 
The  natural  day  and  natu- 
ral year  could  be  appre- 
ciated and  used  long  before 
the  earth's  movements  were 
known  as  their  cause.  It  is 
common  to  call  this  motion 
of  the  earth  its  Eevolution. 
The  path  which  the  earth 
thus  takes  each  year  is 
known  as  its  Orbit.  It  is  almost  a  circle,  but  is  in  fact  an 
ellipse  (see  Fig.  12).  The  sun  is  at  one  focus  of  the  elliptic 
orbit,  about  1,500,000  miles  from  the  center.  It  results 
from  this  that  we  are  about  3,000,000  miles  nearer  the  sun 
on  January  2  than  we  are  six  months  from  that  time.  The 
imaginary  plane  in  which  the  earth's  yearly  path  lies  is  the 
plane  of  its  orbit,  and  is  also  called  the  Plane  of  the  Eclip- 
tic. To  understand  this  statement  it  is  well  to  think  of  the 
plane  as  a  perfectly  flat  surface  of  great  extent,  and  of  the 
orbit  as  a  curve  marked  upon  it.  If  a  boat  sails  around  an 
island,  the  water-surface  represents  the  plane  in  which  it 
travels.  When  the  book  is  so  held  that  this  page  is  flat,  the 
surface  of  the  paper  is  the  plane  of  the  ellipse  in  Fig.  12. 

On  the  equator  a  man  is  carried  through  about  25,000 
miles  a  day  by  reason  of  the  earth's  rotation.  Around  the 
sun  he  travels  nearly  600,000,000  miles  in  a  year.     He  does 


Fig.  12.— The  elliptic  orbit  of  the  earth  and 
its  two  foci.  The  center  is  midway  be- 
tween the  foci.  The  sun  being  at  S, 
the  swinging  earth  is  91,500,000  miles 
distant  at  P  (perihelion)  and  94,500,000 
miles  distant  at  A  (aphelion). 


20      AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

not  feel  either  motion  because  all  his  surroundings,  in- 
cluding the  atmosphere,  go  with  him.  We  have  a  similar 
unconsciousness  when  we  forget  the  motion  of  a  swift, 
smoothly  running  train  until  we  look  through  the  window. 
19.  The  axis  of  the  earth  is  not  perpendicular  to  the  plane 
of  its  orbit. — If  it  were,  the  equator  would  lie  in  the  plane 
of  the  orbit,  or,  in  other  words,  the  plane  of  the  equator 


Fie.  13.— Diagram  to  show  the  attitude  of  the  earth  with  reference  to  tlie  plane  of 

its  orbit. 

would  coincide  with  the  plane  of  the  orbit.  But  in  fact 
the  axis  is  inclined  23 j°  from  the  perpendicular  position,  so 
that  the  equator  lies  half  above  and  half  below  the  orbital 
plane  (see  Fig.  13).  Inclining  thus,  the  axis  of  the  earth 
points  toward  the  pole-star  at  the  north.  Although  the 
earth  swings  in  its  orbit  between  positions  nearly  200,000,000 
miles  apart,  the  star  is  so  enormously  remote  that  it  ever 
seems  in  range  with  the  axis. 

20.  The  turning  of  the  earth  causes  day  and  night.— We 
have  seen  what  are  the  motions  of  the  earth,  and  its  posi- 
tion in  these  motions.  These  are  especially  matters  of 
astronomy,  but  we  are  now  to  see  what  are  the  geographic 
consequences.  The  first  and  simplest  is  named  here.  A 
distant  light  can  shine  on  but  half  of  a  sphere  at  one  time. 
If  the  spherical  earth  were  stationary  in  reference  to  the 
sun's  light,  day  would  be  perpetual  on  one  side  and  night 
on  the  other.     We  may  add  that  the  heat  would  make  life 


THE  EARTH  AND  THE  SUN  21 

impossible  on  the  one  side,  cold  would  prevent  life  on  the 
other,  and  only  a  narrow  zone  might  be  habitable.  The  ro- 
tation of  the  earth  brings  different  parts  in  succession  into 
the  light  and  heat,  and  the  regularity  of  the  rotation  gives 
us  a  uniform  succession  of  days  and  nights. 

21.  The  tipping  of  the  axis  and  the  yearly  revolution  of 
the  earth  cause  the  days  and  nights  to  become  longer  and 
shorter. — This  will  be  best  understood  by  studying  the 
earth  in  several  positions  in  its  yearly  path.  Let  us  first 
take  the  point  at  which  the  north  pole  and  the  northern 
hemisphere  in  general  are  turned  toward  the  sun  (Fig.  14), 
the  point  occupied  by  the  earth  about  June  21.  As  the 
axis  leans  over  to  the  extent  of  23^°,  the  sun's  rays  reach 
to  a,  23^°  beyond  the  north  pole.  Because  the  sun  shines 
across  the  pole  so  far,  we  place  there  what  we  call  the  arctic 
circle,  and  all  points  within  it  have  constant  day  for  a  short 


Fig.  14.— Relation  of  the  earth  to  the  sun's  rays  on  June  21.    The  arrow  near  the 
equator  points  in  the  direction  of  rotation. 

time,  while  the  earth  is  in  that  part  of  its  yearly  journey. 
(Fig.  14  should  be  constantly  consulted.)  If  one  stands  at 
a  at  twelve  o'clock  of  our  night  he  will  then  see  the  "mid- 
night sun"  on  the  horizon  as  he  looks  toward  the  pole. 
In  twelve  hours  he  will  be  at  5,  and  will  see  the  sun  in  the 
south,  47°  above  the  horizon,  or  more  than  half-way  to  the 
zenith,  the  point  directly  above  him. 


22      AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

Let  us  next  consider  c,  some  point  in  the  north  temper- 
ate latitudes.  One  who  has  that  position  at  midnight  will 
be  at  d  twelve  hours  later.  He  will  have  passed  out  of  the 
shadow  and  into  the  light  at  e,  less  than  half-way  from  c  to 
d^  and  his  day  will  therefore  be  longer  than  his  night.  It 
is  for  this  reason  that  our  longest  days  and  shortest  nights 
are  in  the  latter  part  of  June.  Sunrise  occurs  at  e,  and  it  is 
noon  at  d.  At  noon  the  sun  appears  in  the  south,  but  al- 
most up  to  the  zenith.  Standing  at  e,  and  looking  in  the 
direction  of  the  sun's  rays,  we  see  that  the  rising  sun  will 
appear  much  to  the  north  of  east. 

Let  us  now  change  to  a  position  in  which  the  sun  is 
exactly  overhead  at  noon.  We  find  it  at  /,  23|^°  north  of 
the  equator.  Here  we  draw  the  line  which  we  call  the 
tropic  of  Cancer.  Xorth  of  it  the  midday  sun  always  ap- 
pears in  the  south,  but  less  and  less  so  as  we  approach  the 
line.  At  the  equator  it  is  plain  that  the  sun  shines  half 
around  the  earth,  and  day  and  night  are  each  twelve  hours 
long.  We  can  understand  from  our  figure  that  the  day 
about  June  21  varies  from  twelve  hours  at  the  equator 
to  twenty-four  at  the  arctic  circle. 

If  we  turn  to  the  southern  hemisphere  we  find  the  op- 
posite conditions  prevailing.  At  g  on  the  antarctic  circle 
the  sun  is  seen  in  the  north,  on  the  horizon,  once  in  24 
hours.  Within  the  circle  night  reigns  for  the  time.  In 
the  south  temperate  zone  i  marks  sunrise  and  A,  noon.  The 
sun  shines  less  than  half-way  around  the  earth,  hence  the 
days  are  short  and  the  nights  are  long.  The  sun  is  in  the 
north,  and  is  low  in  the  sky,  even  at  noon. 

The  student  should  remember  that  the  account  above 
given  is  wholly  true  only  for  a  short  time  about  June  21. 
He  should  also  take  a  globe,  or  any  ball  marked  like  Fig. 
14  or  Fig.  16,  and  a  lamp,  and  observe  for  himself.  The 
descriptions  of  the  text-book  can  not  supply  clear  ideas 
unless  careful  study  is  also  given. 

In  six  months  the  earth  will  have  moved  to  the  opposite 


THE   EARTH  AND  THE  SUN 


23 


point  in  its  orbit  (December  22  in  Fig.  16).  Its  position 
in  reference  to  the  sun's  rays  is  now  shown  in  Fig.  15.  The 
north  pole  and  northern  hemisphere  are  turned  away  from  the 
The  time  is  about  December  22.     It  is  night  within 


sun. 


1 

^ 

:^^^ 

*       / 

v^ 

>     V 

vSik 

,S'U  N   ,^ 

>      y-> 

vwSk 

jJVft 

n\\\\ 

mM  Plane  of 

^^ 

lllln  ^'"^''' 

' 

llill 

KAV.*; 

.        \ 

fUll 

>        \ 

(iff  ^ 

^       \ 

f      ^"^fof 

^ 

\:>. 

^<- 

/ 

Fig.  15. — Kelation  of  the  earth  to  the  sun's  rays  on  December  22. 


the  arctic  circle,  and  an  observer  on  the  circle,  1,  will  see 
the  sun  on  the  southern  horizon  for  a  few  moments  in  each 
twenty-four  hours.  In  the  temperate  zone  less  than  half  the 
circuit  of  the  earth  is  lighted  at  one  time  by  the  sun  ;  hence 
the  days  are  short  and  the  nights  are  long. .  An  observer  at 
2  sees  the  sun  at  noon  low  in  the  south,  and  when  he  comes 
around  to  sunset,  ^,  it  appears  to  go  down  much  to  the 
south  of  west.  At  the  equator  the  sun  at  noon,  looking 
from  ^  is  still  in  the  south,  but  day  and  night  are  equal  in 
length.  The  noon  sun  is  seen  in  the  south  as  far  south  as 
the  tropic  of  Capricorn,  but  there  it  appears  overhead,  and 
south  of  that  line  it  is  in  the  north.  We  now  find  long 
days  in  the  south  temperate  zone,  and  constant  day,  for  a 
short  time,  within  the  antarctic  circle,  for  the  sun  now 
shines  23|°  past  the  south  pole. 

If  we  could,  about  December  22,  pass  swiftly  from  the 
north  to  the  south  pole,  we  should  begin  our  journey  in  a 
land  of  continuing  night,  passing  to  days  varying  from  a 
few  moments  at  the  arctic  circle  to  twelve  hours  at  the 
equator,  and  thence  to  continuing  day  about  the  south  pole. 


24      AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

In  December  and  June,  therefore,  the  conditions  of  day 
and  night  are  exactly  opposite  in  the  northern  and  southern 
hemispheres.  The  polar  circles  mark  the  limits  to  which 
the  sun  shines  alternately  across  the  poles,  and  the  tropics 
mark  the  north  and  south  bounds  of  the  equatorial  belt  in 
which  the  sun  may  be  seen  directly  overhead. 


Fig.  16.— Illumination  of  the  earth  in  twelve  positions,  corresponding  to  months. 
The  north  pole  is  turned  toward  us. 

The  student  should  consult  again  Fig.  16.  We  are 
now  looking  along  a  line  vertical  to  the  plane  of  the  earth's 
orbit.     We  see  the  position  of  our  globe  on  June  21  and 


THE   EARTH  AND  THE  SUN  25 

December  22,  as  above  described.  Three  months  away,  or 
one-fourth  the  distance  about  the  orbit,  in  either  direction, 
we  see  the  earth  as  it  is  March  21  or  September  23.  Just 
half  of  the  whole  earth  is  lighted  at  once  as  before,  but  the 
light  always  shines  to  both  poles,  and  not  beyond.  Thus, 
whether  one  stood  at  the  arctic  circle  or  in  the  temperate 
zone,  or  at  the  tropic  of  Cancer,  or  on  the  equator,  day  and 
night  would  each  last  twelve  hours.  Hence  these  positions  in 
the  earth's  path  are  the  equinoxes,  or  points  of  equal  nights 
and  days.  These  four  positions  of  the  earth  should  be  well 
understood,  and  then  we  can  appreciate  the  fact  that  the  days 
grow  longer  and  the  nights  shorter  in  the  northern  hemi- 
sphere from  December  until  June,  and  the  reverse  changes 
go  on  from  June  until  December. 

22.  The  changes  of  the  seasons  also  are  due  to  the  inclina- 
tion of  the  axis  and  the  earth's  revolution  about  the  sun. — 
When  the  days  are  long  and  the  sun  rides  high  in  the  sky, 
more  heat  falls  on  the  surface  than  when  the  days  are 
short.  The  air  is  warm,  the  soil  is  warm,  the  clouds  send 
down  rain  rather  than  snow,  plants  thrive,  migratory  birds 
fly  north,  and  we  call  the  time  summer.  It  is  then  winter 
in  the  southern  hemisphere.  Six  months  from  that  time 
the  days  are  short,  the  sun  rides  low,  less  heat  is  received, 
the  air  is  cool,  the  clouds  drop  snow,  and  we  call  the  time 
winter.  The  intermediate  conditions  of  spring  and  au- 
tumn fall  in  the  times  of  more  equal  days  and  nights. 

23.  Zones  of  climate. — When  the  sun  is  low  in  the  sky,  its 
slanting  rays  give  us  less  heat  than  when  it  is  high.  This 
is  illustrated  by  the  cooling  of  the  afternoon  as  the  sun 
descends,  and  it  has  much  to  do  with  the  great  zones  of 
climate.  In  the  arctic  and  antarctic  regions  the  sun's  rays 
always  come  slanting  to  the  surface,  and  warm  it  little. 
Near  the  equator  they  are  always  high,  and  warm  the  sur- 
face much.  Between  the  two  they  change  from  high  in 
summer  to  low  in  winter,  and  warm  the  land  and  sea  mod- 
erately.    Hence  we  speak  of  temperate  zones.     If  the  axis 


26       AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

did  not  tip,  days  and  nights  would  always  be  equal  on  all 
parts  of  the  earth.  The  noonday  sun  would  then  be  always 
at  the  zenith  at  the  equator,  always  on  the  horizon  at  the 
poles,  and  always  at  a  moderate  elevation  in  the  middle 
regions  of  north  and  south.  The  familiar  change  of 
seasons  would  not  exist,  and  the  extremes  of  heat  and 
cold  between  the  equator  and  the  poles  would  be  greater 
than  now.  We  shall  see,  however,  as  we  go  on,  how  the 
climate  of  a  region  depends  on  many  things  besides  its 
latitude. 

24.  Time. — We  have  seen  that  the  rotation  of  the  earth 
gives  a  short  natural  measure  which  we  call  a  day.  And  the 
succession  of  the  seasons,  with  the  passage  of  the  sun  be- 
tween positions  high  and  low,  gives  the  longer  measure 
which  we  call  the  year. 

It  is  plain  that  when  noon  has  come  at  a  given  point, 
say  at  Washington,  it  is  afternoon  for  all  places  east,  and 
before  noon  in  all  places  west.  In  other  words,  each  place 
has  its  local  time.  Xoon  reaches  Washington  forty-three 
minutes  earlier  than  Chicago,  and  more  than  three  hours 
earlier  than  San  Francisco.  For  each  fifteen  degrees  of 
longitude  there  is  a  difference  of  one  hour  in  local  time.  If 
time  were  kept  only  by  stationary  clocks,  these  differences 
would  cause  no  practical  inconvenience,  and  in  fact  they 
received  little  attention  so  long  as  journeys  were  rare  and 
slow ;  but  with  the  general  carrying  of  watches  and  with 
great  increase  of  travel  they  became  a  source  of  much  an- 
noyance and  difficulty.  Each  railway  company  set  all  its 
clocks  and  watches  to  correspond  to  local  time  at  some  one 
station  and  there  was  a  difference  between  local  time  and 
"  railroad  time  "  at  every  other  station.  To  escape  such 
confusion  the  system  of  Standard  Time  was  adopted.  Un- 
der that  system  the  country  is  divided  into  north  and  south 
belts  fifteen  degrees  broad,  and  all  parts  of  each  belt  use 
the  time  which  is  local  for  places  on  the  central  meridian 
of  the  belt.     The  times  in  two  adjacent  belts  differ  by  just 


THE  EARTH  AND  THE  SUN  27 

one  hour.     In  the  following  list  of  standard  time  districts 
the  degrees  mark  west  longitude : 

Intercolonial 52.5°  to    67.5°. 

Eastern 67.5°  to    82.5°. 

Central........ 82.5°  to    97.5°. 

Mountain 97.5°  to  112.5°. 

Pacific .112.5°  to  127.5°. 

25.  Summary. — The  earth  is  one  of  a  family  of  planets, 
each  pursuing  a  nearly  circular  path  about  the  sun.  Being 
very  small  as  compared  with  its  distance  from  the  sun,  it 
receives  but  the  smallest  fractions  of  the  sun's  light  and 
heat,  but  these  are  all-important  to  the  earth,  and  make  its 
life  possible.  The  rotation  of  the  earth  causes  day  and 
night.  The  inclination  of  the  axis,  combined  with  the  an- 
nual revolution,  causes  the  changes  in  the  length  of  day 
and  night,  and  the  succession  of  the  seasons.  These  changes 
alternate  between  the  northern  and  southern  hemispheres. 
Our  measures  for  duration,  or  the  passage  of  time,  are 
found  in  the  periods  required  for  the  two  great  movements 
of  the  earth. 


CHAPTER  III 

RIVERS 

26.  Terms. — We  begin  our  study  of  rivers  by  looking  at 
a  narrow  valley.  We  often  call  such  a  valley  a  Gorge,  re- 
ferring to  its  depth,  or  throat-like  form;  or  a  Eavine,  a 
word  which  means  a  narrow  passage  worn  by  swift  waters. 
A  Gully  is  a  small  ravine,  like  a  deep  ditch;  Canyon  is 
commonly  used  of  great  gorges  in  the  western  United 
States ;  while  Gulch  is  a  name  often  given  to  gorges 
in  western  mining  regions.  Glen,  Dale,  and  Dell  are 
somewhat  poetic  words  for  small  valleys  secluded  among 
hills. 

27.  A  gorge. — Let  us  choose  any  gorge,  large  or  small, 
which  we  know  best,  and  enter  it.  No  two  will  be  alike, 
yet  some  of  the  same  things  will  be  seen  in  all.  It  may  be 
50,  100,  300,  or  500  feet  deep.  If  we  are  among  the  west- 
ern mountains  and  plateaus  there  will  be  some  greater 
gorges,  even  to  a  mile  in  depth.  The  gorge  may  have  ver- 
tical walls  on  either  hand.  If  so,  we  shall  nearly  always 
find  the  solid  rocks  exposed,  and  these  rocks  often  con- 
sist of  layers  or  beds.  The  beds  vary  in  thickness  from 
an  inch  or  two  to  several  feet,  and  often  some  are  harder 
than  others.  In  this  case  they  will  stand  in  relief,  while 
the  soft  beds  are  crumbling  away.  If  the  rocks  are  not 
much  decayed,  they  often  show  even  faces  of  considerable 
size,  standing  up  like  a  wall  of  masonry  in  which  each 
block  has  been  smoothly  dressed.  Such  faces  are  caused 
by  straight  cracks  or  partings  in  the  rocks  called  joints, 
and  when  the  rocks  lie  in  horizontal  beds,  the  joints  are 

28 


klVERS 


^d 


about  vertical.  They  make  it  possible  for  gorges  to  have 
perpendicular  cliffs  (see  Fig.  17). 

Two  sets  of  joints  commonly  cut  each  other  nearly  at 
a  right  angle,  hence  it  is  that  niches  and  buttresses  in  great 
variety    often    develop 
along    the    sides    of    a 
gorge. 

But  the  walls  are  not 
usually  vertical  from 
bottom  to  top.  We  may 
often  climb  over  a  slope 
of  waste  that  has  fall- 
en from  above.  Such  a 
slope  of  waste  is  called 
a  Talus,  because  in  form 
it  resembles  the  ankle. 
It  may  consist  of  fine, 
sliding  fragments  not 
yielding  secure  footing ; 
or  we  may  find  a  rough 
but  solid  path  over 
large  blocks  of  rock. 
Whether  the  talus  be 
steep  or  not,  and  wheth- 
er it  be  of  fine  or  coarse 
material,  will  depend  on 
the  nature  of  the  rocks 
in  which   the  gorge  is 

cut.  Eising  from  the  top  of  the  talus  is  often  a  vertical 
cliff,  at  the  foot  of  which  one  may  pick  his  way  for  a  long 
distance  without  finding  a  path  to  the  top. 

Most  gorges  have  more  or  less  sloping  sides.  This  is 
partly  due  to  the  talus,  as  already  described.  It  is  also 
caused  by  the  crumbling  of  the  upper  walls,  as  blocks  of 
rock  are  wedged  off  by  frosts  or  pushed  down  by  the 
growing  roots  of  trees,  which  in  such  places  thrust  them- 


FiG.  17.— Gorge  of  Temple  Creek,  Utah.  The 
cliff  at  left  is  a  joint  plane  ;  other  joints 
divide  the  distant  cliff  into  vertical  slabs. 
The  creek  is  now  small  and  doing  little 
work,  but  in  flood  time  it  has  rolled  even 
the  great  boulder  at  the  right. 


Fig.  18.— Canyon  of  the  VcUowstoiR',  a  V-jjorge,  showing  crags  aud  Uilus  blopcs. 
30 


RIVERS  31 

selves  into  cracks  and  apply  great  pressure.  A  gorge  with 
evenly  sloping  sides  is  often  called  V-shaped,  and  the  V  is 
narrow  or  broad,  according  to  the  amount  of  wasting 
which  has  taken  place. 

A  gorge  may  have  in  general  the  V  form,  but  show  some 
irregularities.  If  a  hard  layer  of  rock  ten  feet  thick  lies 
between  softer  beds  it  will  stand  out  and  form  a  small 
cliff  on  the  slope.  Thus  we  may  have  short  slopes  alter- 
nating with  low  cliffs  on  the  sides  of  the  gorge.  The 
cliffs  mark  the  hard  beds,  and  the  slopes  are  formed  of 
waste  veneering  the  edges  of  the  soft  beds  (Fig.  64  and 
frontispiece). 

If  the  gorge  is  excavated  in  softer  material,  such  as  clay 
or  sand,  we  may  find  very  smooth  and  symmetrical  slopes 
perfectly  illustrating  the  V  form.  Such  slopes  show  in- 
clinations of  30°  to  40°  with  the  horizon. 

A  multitude  of  small  gorges  can  receive  no  notice  here, 
but  are  of  local  interest  and  of  value  to  students  of  geogra- 
phy. As  examples  of  great  gorges  in  the  East  we  may  name 
the  Kanawha,  the  Hudson  in  the  Highlands,  the  Deerfield, 
and  the  Saguenay.  Here  may  be  mentioned  also  the  short 
gorges  or  "  water  gaps  "  of  the  Delaware  at  Stroudsburg, 
the  Susquehanna  at  Harrisburg,  and  the  Potomac  at  Har- 
pers Ferry.  All  these  are  flaring  and  of  considerable 
age.  The  Niagara,  the  Mississippi  at  Minneapolis,  Ausable 
Chasm,  and  Watkins  Glen  are  examples  of  younger,  steep- 
walled  gorges. "  The  Yellowstone,  the  Eoyal  Gorge  of  the 
Arkansas,  the  Black  Canyon  of  the  Gunnison,  and  the 
Grand  Canyon  of  the  Colorado,  are  examples  of  the  pro- 
found river  gorges  of  the  western  United  States. 

28.  The  stream. — Along  the  bottom  of  every  gorge  is  a 
stream  channel.  In  it  may  flow  a  great  river  or  a  brook  or 
only  a  temporary  torrent.  The  stream  is  there  because  the 
slopes  of  the  land  guide  the  water  that  way,  and  the  stream 
may  thus  be  said  to  exist  on  account  of  the  channel.  But 
in  an  equally  important  way  the  gorge  exists  because  of 
4 


S2      AN  INtRODtJCTlON  TO  1>HYSICAL  GEOGRAPHY 

the  stream,  for  the  stream  is  in  fact  the  maker  of  the 
gorge  and  is  still  at  work  on  it,  deepening  and  enlarging. 
Let  ns  look  at  the  stream.  We  shall  often  find  it  a  roaring 
torrent  in  April  and  May,  and  only  a  rivnlet  making  its 
way  among  the  stones  in  Angust  or  September.  In  many 
ravines  the  bed  is  dry  during  the  summer  months,  except 
after  a  heavy  shower  or  long  rain.  Then  the  water  quickly 
gathers  from  the  fields  and  rolls  yellow  and  muddy  where 
just  before  a  dry  path  led  up  over  the  pebbles  of  the  stream 
bed.  This  suggests  that  during  the  breaking  up  of  the 
spring,  and  after  the  heavy  rains  of  summer  and  autumn, 
the  stream  does  most  of  its  carrying  work. 

Let  us  examine  the  bed  of  the  stream.  We  shall  often 
find  a  floor  of  rock.  If  the  stream  shows  such  a  floor, 
we  may  know  that  it  is  effectively  carrying  away  the 
waste  which  is  supplied  up-stream  by  the  breaking  up  of 
rocks.  The  flood  current  is  so  swift  and  strong  in  volume 
that  little  rocky  rubbish  can  rest  in  its  path.  This  also 
means  that  the  rocks  of  the  stream  bed  are  exposed  to 
wear  whenever  the  current  is  strong.  They  are  filed  down 
by  the  sand  and  pebbles  that  sweep  across  them.  Their 
surfaces  are  dissolved  and  the  fine  matter  is  borne  away. 
Flakes  and  blocks  of  the  rock  loosen  by  frost  in  winter,  and 
are  hurried  off  by  the  floods  of  spring.  Thus  the  gorge  is 
growing  deeper  by  the  wearing  of  its  floor. 

But  on  either  side  will  often  lie  banks  of  waste  at  the 
foot  of  the  cliffs.  These  will  be  more  or  less  attacked,  ac- 
cording to  the  power  of  the  stream.  And  at  some  points 
of  less  slope  the  bed  of  the  stream  will  be  covered  with 
shingle,  or  coarse,  rough  waste.  And  in  some  still  pools, 
sand  and  mud  will  gather,  until  the  down-stream  rim  of  the 
little  basin  is  cut  away.  Thus  the  bed  will  be  protected  at 
some  points  and  subject  to  wear  at  others.  Depressions 
are  gradually  filled,  jutting  ledges  are  worn  away,  and  the. 
bed  of  the  stream  gains  a  smooth  grade. 

If  we  find  the  floor  of  the  stream  covered  with  waste, 


t^^ 


Fig.  19— a  small  river  at  low  stage.  The  water  is  clear.  The  shore  at  the  bend 
shows  bed-rock,  but  the  river  bottom  near  by  is  covered  by  loose  blocks  (boul- 
ders) which  have  been  rounded  by  rolling. 

33 


34       AN  INTRODUCTION  TO   PHYSICAL   GEOGRAPHY 

this  means  that  the  crumbled  rock}^  matter  is  supplied 
faster  than  the  stream  can  carry  it  away.  Thus  a  river  or 
brook  may  be  overloaded — that  is,  so  charged  with  land 
waste  that  instead  of  filing  the  rocky  channel,  it  casts  down 
a  protecting  blanket  of  mud  and  stones  upon  it.  This, 
however,  does  not  happen  so  often  in  gorges  as  along  the 
bottoms  of  open  valleys  where  the  flow  is  less  swift. 


Fig.  20.— Ice-jam,  Red  River,  Manitoba. 

The  student  should  see  that  some  of  the  stones  in  the 
stream  bed  are  angular,  and  some  have  the  corners  re- 
duced, or  are  well  worn  and  rounded.  These  differences 
depend  on  the  varying  distance  along  which  the  cur- 
rent has  pushed  and  rubbed  the  fragments.    All  the  finer 


EIYERS  35 

rock  flour  thus  made  has  been  easily  swept  down  the 
stream  and  is  resting  in  the  banks,  or  -has  been  carried  out 
and  spread  over  the  floor  of  the  sea. 

These  are  the  ways  in  which  a  stream  works  on  the  bed 
of  its  channel :  by — 

1.  Filing  with  sand  and  pebbles. 

2.  The  dissolving  of  rock  by  the  water. 

3.  Ice-push  of  blocks  of  rock  in  the  spring. 

4.  The  heaving  of  blocks  by  water  freezing  in  cracks. 
And  also,  as  a  carrier,  it  removes  the  rock  chips  its  tools 

have  loosened.  Little  by  little,  year  by  year,  century  by 
century,  it  works  away,  grinding  and  sawing  its  bed  and 
making  the  gorge  deeper. 

The  widening  of  the  gorge  or  valley,  due  partly  to  the 
stream  and  partly  to  weathering,  will  be  described  in  later 
sections. 

29.  Sources  of  the  water. — Having  studied  the  gorge 
and  the  work  of  the  water  flowing  in  it,  let  us  inquire  for 
the  sources  of  the  water.  It  all  comes  at  first  from  the 
sea,  or  in  less  degree  from  lakes  and  rivers,  by  evapora- 
tion, by  the  formation  of  clouds  and  the  fall  of  rain.  On 
all  land  surfaces  the  water  tends  to  gather,  to  flow  along 
the  lines  of  greatest  slope,  to  form  rills  at  first  and  then 
larger  streams.  As  soon  as  a  stream  of  any  size  has  formed 
on  a  sloping  surface,  gorge-making  begins.  But  rain- 
water does  not  all  flow  directly  into  surface  streams.  Much 
of  it  soaks  into  the  soil  and  often  deep  into  the  rocks,  and 
comes  out  in  the  form  of  springs.  The  journey  under- 
ground may  cover  a  few  rods  or  many  miles.  Great  cav- 
erns may  be  made  by  solution  and  by  wear  of  the  waters,  and 
springs  of  great  volume,  even  to  thousands  of  gallons  per 
minute,  may  boil  up  at  the  surface  and  set  in  motion  a 
large  surface  stream  at  once. 

In  regions  of  cold  winters  much  water  lies  on  the  sur- 
face as  snow  until  the  coming  of  spring,  and  then  melts 
quickly,  and  thus  floods  are  larger  and  more  valley-making 


36      AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

is  accomplished  than  would  be  possible  if  the  water  fell  as 
rain  and  ran  freely  away  after  each  storm. 

As  we  have  jast  seen,  only  a  part  of  the  falling  rain 
runs  directly  away.  If  the  soils  and  rocks  are  porous,  or 
the  surface  is  flat,  or  the  air  very  dry,  less  runs  away 
than  if  the  rocks  are  hard,  the  surfaces  steep,  and  the  air 
moist.  Hence  it  is  that  the  percentage  of  "  run-off  "  to  the 
entire  amount  of  rain  varies  from  one-third  or  two-fifths  in 
New  England  to  one-quarter  in  the  Mississippi  valley,  and 
much  less  in  the  dry  regions  of  the  world. 

30.  River  basins. — The  amount  of  water  forming  a  given 
stream  also  depends  on  the  size  of  the  Basin.  The  basin 
of  a  river  includes  all  the  land  surface  which  inclines  toward 
it,  and  whose  surplus  waters  enter  the  ocean  or  trunk  stream 
by  it.  A  river,  then,  in  the  true  sense  includes  all  its  branches 
however  small,  and  a  river  system  is  a  tree-like  group  of 
streams  reaching  down  to  the  ocean  by  one  trunk. 

31.  Divides. — The  boundary  between  the  basins  of  two 
adjoining  streams  or  stream  systems  is  called  a  Divide,  be- 
cause the  water  falling  as  rain  is  there  divided,  part  of  it 
going  to  one  stream  and  part  to  the  other.  A  divide  is  the 
higher  land  forming  the  watershed  or  water-parting  be- 
tween two  river  basins.  It  may  follow  the  crest  of  a  ridge, 
high  or  low,  or  it  may  traverse  a  plain  so  level  that  its 
course  is  uncertain  or  even  variable.  The  very  flat  region 
at  the  head  of  the  Illinois  and  Chicago  rivers,  now  crossed 
by  the  Drainage  Canal,  illustrates  the  flexible  meaning  of 
the  word  divide.  The  streams  that  enter  Lake  Ontario 
from  New  York  are  not  separated  from  the  Susquehanna 
and  Alleghany  by  a  ridge,  but  there  is  an  interlocking  sys- 
tem of  head-waters,  in  which  the  local  divides  are  some- 
times hill  ridges,  and  sometimes  flat  and  swampy  areas  in 
valleys.  It  is  stated  that  small  steamers  may,  in  high  wa- 
ter, pass  between  the  Mississippi  and  the  Eed  River  of  the 
North.  In  high  mountain  regions  where  the  divide  is  usu- 
ally a  sharp  edge,  it  is  rarely  straight  for  any  distance,  but 


Fig.  21.— Cascade,  due  to  joints  and  bedding  planes.  Fall  Creek,  near  Ithaca,  N.  Y. 
In  the  foreground  is  a  pot-hole  whose  walls  have  been  partly  broken  away.  See 
pages  38  and  41. 

37 


38       AN  INTRODUCTION  TO   PHYSICAL  GEOGRAPHY 


full  of  sharp  curves  and  zigzags.  As  there  are  divides  sep- 
arating river  systems,  so  there  are  subordinate  divides  be- 
tween different  branches  of  the  same  system. 

32.  Waterfalls  and  rapids. — These  are  common  in  gorges. 
A  series  of  falls  with  alternating  rapids  will  often  be  found. 

Water  pouring  over  sin- 
gle beds  or  steps  of  the 
rock  forms  low  falls. 
Strong  rapids  occur  in 
the  Grand  Canyon  of  the 
Colorado,  opposite  the 
mouths  of  tributaries. 
These  side-streams  have 
brought  great  boulders 
down  their  steep  torrent 
beds,  and  heaped  them 
in  the  main  channel  as 
barriers  over  which  the 
trunk  river  plunges. 

Falls  of  considerable 
height  are  formed  in 
various  ways.  If  well- 
developed  joints  cross 
the  track  of  the  stream, 
the  blocks  wear  away 
up-stream  to  a  given  joint,  which  maintains  a  wall  over 
which  the  water  descends.  With  several  joint  planes 
and  the  planes  of  bedding,  a  stairway  is  often  made  over 
which  the  water  cascades  to  the  bottom.  If  softer  beds 
of  rock  are  capped  by  a  hard  layer,  the  decay  of  the  soft 
beds  and  the  blows  given  them  by  the  falling  water  cut 
them  back  and  leave  the  hard  sheet  projecting  over  them, 
thus  giving  the  waters  a  single  plunge  to  the  bottom. 
This  is  the  way  in  which  Niagara  is  formed.  There  the 
rocks  are  nearly  horizontal.  The  falls  are  about  160  feet 
in  height.     Sixty  feet  or  more  of  the  upper  rocks  are  hard. 


Fig.  22.— a  limestone  boulder  in  the  bed  of 
the  Colorado  at  a  rapid.  During  floods 
sand  is  swept  over  it  (from  right  to  left), 
grinding  and  carving  it. 


FiQ.  23.— A  waterfall  near  Gadsden,  Ala.  A  strong  layer  of  sandstone  projects  like  a 
cornice  because  the  soft  shale  beneath  has  been  eaten  away.  The  fallen  blocks  are 
angular  because  not  rolled  by  the  stream.  The  deep  hollow  under  the  fall  contains  a 
pool  of  still  water.  The  stream  is  now  small.  In  flood  it  spreads  over  the  bare  rock 
to  the  edge  of  the  forest,  and  plunges  with  great  force  to  the  bottom  of  the  pool. 

59 


RIVERS 


41 


thick  beds  of  limestone.  For  the  most  part,  the  rocks  below 
these  are  shales  or  hardened  muds.  These  wear  back,  as 
shown  in  the  diagram  (Fig.  25).  As  the  foundation  is  re- 
moved, great  blocks  of 
the  hard,  capping  rock 
fall  down.  Thus  the  form 
of  the  falls  changes,  and 
they  are  receding — that 
is,  the  gorge  is  growing 
longer  at  the  south  end, 
as  the  falls  slowly  move 
up  the  river  toward  Buf- 
falo. The  rate  of  reces- 
sion is  four  to  five  feet 
per  year.  In  such  a  fall 
the  water  strikes  the  bot- 
tom with  great  force,  and 
tears  or  wears  the  rock. 
Hence  a  pool  is  formed. 

At  the  base  of  the  Horseshoe  Fall  the  water  is  about  200 
feet  deep.  At  the  base  of  some  small  falls  in  Watkins  Glen, 
fine,  well-like  pools,  six  to  ten  feet  deep,  with  vertical  rock 
walls,  are  seen.  These  smaller  pits  in  stream  beds  are  known 
as  pot-holes,  and  may  be  found  in  the  rocky  floor  of  almost 
any  swift  stream.  They  vary  in  diameter  from  a  few  inches 
to  several  feet,  and,  if  large,  may  be  20  feet  deep  or  more. 
They  are  drilled  down  by  pebbles  or  larger  stones  whirled 
by  the  dashing  and  rushing  waters  (Figs.  21  and  108). 

Over  the  sides  of  ravines  small  waterfalls  are  often  found. 
This  means  that  the  main  stream  has  sunk  its  channel  more 
rapidly  and  deeply  than  the  side-stream.  Where  the  Co- 
lumbia River  has  opened  a  gorge  through  the  Cascade  range 
the  valleys  of  two  creeks  end  high  on  the  wall,  and  their 
leaping  waters  break  into  spray  like  the  Bridal  Veil  Fall 
of  the  Yosemite.  The  Latonrelle  is  260  feet  high  and  the 
Multnomah  600. 


Fig.  25.— Diagram  showing  the  appearance  of 
rocks  and  stream  if  a  deep  cutting  (section) 
were  made  at  Niagara  Falls.  Upper  lime- 
stone about  60  feet  thick.  Water  below  the 
fall,  200  feet  deep.  Boulders,  tumbled  about 
by  the  water,  help  to  wear  the  shale. 


42      AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

While  waterfalls  are  most  numerous  along  small  streams 
and  in  the  lesser  gorges,  we  see  in  the  case  of  Niagara 
that  great  streams  may  fall.  The  Mississippi  at  Minne- 
apolis forms  the  Falls  of  St.  Anthony.  Here  also  the  cap- 
ping rock  is  limestone,  but  thinner  than  at  Niagara.  Sho- 
shone Fall  in  Idaho  is  similar  in  origin,  but  in  this  case  the 
'hard  bed  over  which  the  Snake  River  plunges  is  a  horizon- 
tal sheet  of  cooled  lava. 

33.  Man's  use  of  waterfalls. — Where  a  stream  descends 
quickly,  it  is  possible  to  divert  it  from  its  bed,  carry  it  a 
short  distance  in  a  canal  or  flume,  and  use  it  to  turn  the 
wheels  of  shops  and  factories ;  and  the  sites  of  waterfalls 
are  especially  favorable  for  such  utilization.  The  primi- 
tive grist-mill  and  sawmill  are  followed  by  larger  under- 
takings, and  towns  and  cities  grow  where  nature  offers 
power  to  help  man's  work.  It  was  about  mill-wheels  that 
Lowell  and  Lawrence,  Fall  River  and  Holyoke  grew  in 
New  England,  Rochester  in  New  York,  and  Minneapolis  in 
Minnesota.  The  power  of  Trenton  Falls  is  used  in  Utica ; 
a  thread  of  Niagara's  great  volume  turns  wheels  of  neigh- 
boring shops  and  lights  the  streets  of  Buffalo,  and  the  swift 
streams  of  the  Southern  Appalachians  are  harnessed  to  do 
the  work  of  man.  On  the  border  of  the  campus  of  Cornell 
University  a  waterfall  in  a  deep  gorge  has  been  put  to  use 
by  the  building  of  a  unique  structure,  a  hydraulic  labora- 
tory, in  which  all  the  problems  arising  from  the  use  of 
water  for  power  may  be  subjected  to  experiment  and  exact 
study.  Thus  the  force  of  the  earth  is  linked  to  the  thought 
and  enterprise  of  man. 

34.  Alluvial  fans  or  cones. — Where  a  gorge  passes  into 
an  open  valley  one  often  finds  a  gathering  of  land  waste 
having  the  form  of  a  fan,  with  the  apex  pointing  up  the 
gorge.  From  the  apex  toward  the  border  the  slope  may 
be  gentle  or  quite  sharp.  If  the  grade  in  the  gorge  is 
steep,  the  swift  waters  will  bring  out  coarse,  bouldery 
waste  and  drop  it  suddenly,  making  a  steep  fan.     If  the 


RIVERS 


43 


grade  is  less,  finer  material  will  come  down  and  be  carried 
farther  out  on  the  floor  of  the  trunk  valley,  giving  a  wide 
fan  of  small  slope.  The  stream  flows  sometimes  along  one 
radius  of  the  fan  and  sometimes  on  another,  thus  building 
up  all  parts  in  succession.  Such  a  body  of  waste  forms  a 
more  or  less  perfect  segment  of  a  low  cone ;  hence  the 
term  Alluvial  Cone  is  often  used.     In   a  mountain  land 


Fig.  26.— An  alluvial  cone.    Near  Great  Salt  Lake,  Utah. 


like  Switzerland  such  cones  are  common  and  large,  and  a 
thrifty  people,  desiring  every  possible  acre  of  land  for  till- 
age, confine  the  lawless  torrent  in  a  single  channel  of  ma- 
sonry. Thus  they  "  rectify "  the  stream,  clear  away  the 
boulders,  and  gather  good  harvests  from  what  seems  for- 
bidding ground. 

35.  Development  of  a  valley.— Let  us  now  recall  the  fact 
that  of  the  gorges  of  V-shape  some  are  more  open  than 
others.  The  upper  slopes  of  such  gorges  are  often  well 
rounded.  As  time  goes  on,  much  rock  weathers  away  on 
the  sides  of  the  valley,  and  steadily  slips  down  toward  the 
stream  and  is  carried  away.     Thus  by  degrees  the  gorge  be- 


44      AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

comes  an  open  valley.  It  is  profitable  to  picture  to  our- 
selves such  growth  of  a  wide  valley  out  of  a  narrow,  steep- 
walled  gorge.     And  it  is  well  in  our  walks  and  travels  to 


Fig.  27.— Profiles  across  a  valley  at  different  stages  of  development. 

watch  for  valleys  which  are  neither  very  narrow  nor  very 
wide,  but  are  in  middle  stages  of  growth. 

36.  Open  valleys. — As  the  valley  broadens,  the  slopes  of 
the  valley  sides  become  gentle.  Here  and  there  may  be 
steep  bluffs  of  small  extent,  but  the  general  inclination  is 
quite  moderate.  In  field  excursions  cross  profiles  of  nar- 
row and  wide  valleys  should  often  be  drawn.  On  the 
sides  of  open  valleys  rocky  ledges  may  occur,  showing  that 
a  perfect  grade  has  not  been  reached.  But  with  time 
enough,  such  ledges  will  crumble  and  a  perfect  slope  of 
soil  or  coarser  waste  will  appear. 

The  river  in  such  a  valley  commonly  flows  on  a  floor  of 
waste  which  it  has  laid  down.  Here  and  there  it  may 
cross  rocky  ledges,  giving  rise  to  rapids  such  as  are  more 
commonly  seen  in  gorges.  Above  each  rapid  is  a  stretch 
of  nearly  still  water,  giving  us  an  alternating  series  of  rap- 
ids and  "  reaches."  Hence  the  "  portages  "  so  common  in 
canoeing  trips,  and  which  form  a  feature  in  primitive  car- 
riage of  goods  by  water.  Many  of  these  portages,  as  at  Little 
Falls  and  Cohoes  on  the  Mohawk,  were  early  superseded  by 
canals.  Even  if  there  are  no  ledges  of  rock,  there  are  still 
alternations  of  rapid  and  reach;  but  these  are  low-water 
features  only.  At  high  stage  the  forward  slope  of  the 
water  surface  is  nearly  even,  but  there  are  differences  in 
the  current,  causing  bars  of  waste  to  form  here  and  there ; 
and  at  each  of  these  bars  a  rapid  appears  when  the  flood 
has  passed.  It  is  instructive  to  study  a  familiar  creek  when 
its  banks  are  full,  and  see  how  little  trace  remains  of  well- 
known  deeps  and  shoals. 


RIVERS 


45 


A  large  river  may  be  many  feet  deep,  and  is  often  a  half- 
mile  or  more  in  width.  A  few  great  rivers  like  the  Ama- 
zon show  a  width  of  many  miles  at  their  seaward  ends. 
The  stream  is  bordered  by  banks  varying  from  a  few  feet  to 
twenty  or  more  in  height.  These  banks  are  the  edges  of 
nearly  flat  grounds  which  stretch  away  to  the  base  of  the 
valley  slopes.     These  are  known  as — 

37.  Flood-plains. — Commonly  the  water  is  confined  be- 
tween the  banks,  but  in  the  spring,  or  after  great  rains,  the 
stream  passes  its  banks  and  floods  the  strips  of  flat  ground 


Fig.  28.— Flood-plain  of  the  James  River,  Va. 

on  either  hand.  At  such  times  the  river  is  charged  with 
mud,  and  a  layer  of  this  fine  material  is  spread  over  the 
flooded  grounds.  Thus  when  the  water  retires,  it  leaves 
them  a  little  higher  than  before.  The  deposit  consists  of 
fine  waste,  largely  derived  from  soils  of  the  uplands.  It 
thus  constantly  adds  to  the  fertility  of  the  lowlands,  which 


46       AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


bear  rank  forests,  and  when  these  are  cleared  yield  peren- 
nial harvests.  They  are  easily  tilled,  and  are  usually  the 
lands  first  occupied  in  a  new  country.  Their  smooth  sur- 
faces offer  natural  grades  for  the  primitive  wagon  and  stage, 


ijiiiaaiii 


Fig.  29.— Scene  on  the  Mississippi  during  a  great  flood.    Overflowing  a  levee,  the 
water  tears  out  a  section  of  it  and  spreads  over  the  plain. 

as  for  the  railway  of  later  days.  If  the  stream  is  navigable, 
the  products  of  the  valley  may  be  easily  and  cheaply  ex- 
changed for  needed  articles  from  distant  regions.  A  large 
share  of  the  population  of  most  countries  is  found  on  the 
flood-plains  of  rivers.  These  strips  of  low  ground,  there- 
fore, have  great  interest  to  the  geographer.  The  student 
should  examine  the  atlas  sheets  of  the  United  States  Geo- 
logical Survey  for  these  forms.  The  Missouri  River  in 
Missouri  will  be  found  to  have  flood-plains  varying  from  IJ 
to  8  miles  in  width.  The  flood-plains  of  the  Illinois  Eiver 
are  more  than  a  mile  wide  at  Lasalle  (see  map.  Fig.  11) 
and  Ottawa  and  are  three  miles  wide  at  Chillicothe.     That 


RIVERS 


47 


of  the  Mississippi  is  6  miles  wide,  near  Clinton,  Iowa,  and 
much  wider  than  this  in  its  lower  course.  The  middle 
Ehine  exhibits  one  of  the  most  carefully  tilled  and  thickly 
settled  flood-plains  of  Europe,  while  Egypt  as  a  habitable 
and  productive  land  consists  chiefly  of  the  flood  and  delta 
plains  of  the  Xile. 

Along  a  large  river  the  flood-plain  is  higher  next  the 
stream,  because  there  the  waste  first  lodges  in  times  of  over- 
flow, and  the  plain  slopes  gently  thence  to  the  valley  sides. 
Such  a  strip  of  higher  ground,  from  its  resemblance  to  a 
dike  thrown  up  to  restrain  floods,  is  called  a  "  natural  levee." 
It  often  happens  that  the  outer  parts  of  the  plain  are  flooded 
while  long  strips  of  natural  levee  appear  between  the  back 
water  and  the  main  channel,  and  therefore  the  farmers  of  a 
great  flood-plain  build  their  houses  close  to  the  river. 


Fig.  30.— Scene  on  the  flood-plain  of  the  Mississippi  after  a  break  in  the  levee. 


38.  Floods. — Since  so  many  people  live  on  flood-plains 
and  the  most  important  industries  of  town  and  country  are 
5 


48       AN  INTRODUCTION  TO   PHYSICAL  GEOGRAPHY 

often  centered  there,  floods  become  most  destructive,  and  to 
deal  with  them  is  a  problem  of  greatest  importance.  The 
Genesee,  usually  a  little  river,  is  sometimes  two  miles  wide 
on  its  flood-grounds  in  Livingston  County,  and  occupies, 
once  or  twice  in  a  generation,  streets  and  stores  in  Koches- 
ter.  The  Ohio  River,  fed  by  swift  streams,  rises  50  feet 
above  its  normal  surface  at  Cincinnati.  The  Mississippi, 
enlarged  by  the  melting  snows  of  the  Appalachians  and  the 
Rocky  Mountains,  is  subject  to  enormous  floods.  The  great 
flood  of  1897  covered  13,000  square  miles,  and  destroyed 
$15,000,000  worth  of  property.  This  flood  was  carefully 
studied,  and  the  official  report  upon  it,  issued  by  the  United 
States  Weather  Bureau,  forms  a  large  volume.  The  Weather 
Bureau  is  able  in  some  measure  to  predict  such  floods,  to 
the  saving  of  much  life  and  property. 

We  should  not  forget,  however,  that  floods  are  beneficent, 
since  river  plains  are  made  and  kept  fertile  by  them.  The 
annual  flood  of  the  Nile,  rising  25  feet  at  Cairo,  enriching 


Yellowstone  Park. 


and  watering  the  land  and  supporting  millions  of  people,  is 
a  conspicuous  illustration.  The  evils  of  floods  are  to  be 
largely  escaped  by  prediction,  by  the  making  of  levees,  by 


RIVERS 


49 


protecting  river-banks  against  wear,  and  by  avoiding  the 
lowest  levels  in  the  making  of  homes.  We  should  not  for- 
get to  observe  that  a  river  which  passes  through  great  lakes, 
as  the  St.  Lawrence,  has  its  flow  equalized,  and  its  lower 
course  is  thus  free  from  floods. 


Fig.  32.— Junction  of  the  Mississippi  and  Arkansas  rivers  ;  showing  meanders,  ox- 
bow lakes,  and  river  swamps.  The  swing  of  the  meander  is  in  proportion  to  the 
size  of  the  river.    Scale,  1  inch  =  7  miles. 

39.  Meanders. — Many  rivers,  as  they  traverse  their  flood- 
plains,  swing  to  right  and  left  in  strong  curves.  Thus  the 
distance  from  Cairo,  111.,  to  the  Gulf  of  Mexico  is  about 
500  miles,  but  by  the  river  one  travels  over  1,000  miles. 
The  breadth  of  these  swings  of  the  Mississippi  is  from 
3  to  6  miles.  On  the  outside  of  the  curves  there  is  deep 
water  and  a  steep  bank,  at  which  landings  are  possible 
for  steamboats.  On  the  inner  side  is  a  sloping  beach  pass- 
ing beneath  shallow  water.  The  river  cuts  away  the  outer 
shore  and  adds  to  the  other,  and  thus  widens  the  belt  of 
curves  or  Meanders,  as  they  are  called,  from  a  winding  river 


5  s 

'O    o 


P.  <i> 


RIVERS 


51 


of  Asia  Minor.  Little  by  little,  however,  the  tongue  of  land 
that  reaches  into  a  great  bend  is  narrowed  at  its  base,  by  the 
growth  of  other  bends,  until  at  last  the  neck  is  cut  away, 
and  the  river  track  is  shortened.  By  such  a  "  cut-off  "  of  one 
of  the  great  Mississippi  meanders,  the  river  may  be  shortened 
at  a  given  point  by  15  or  20  miles.  The  curving  channel 
thus  abandoned  by  the  current  is  soon  partitioned  from  the 
river  by  the  growth  of  a  bar- 
rier of  waste,  and  becomes  an 
"  ox-bow  "  lake  (Fig.  32). 

The  Mississippi  has  been 
taken  as  an  example,  and 
there  is  advantage  in  its 
study  because  its  importance 
has  caused  the  making  of 
elaborate  maps,  but  the  me- 
andering habit  is  not  limited 
to  great  rivers.  It  is  as  per- 
fectly seen  in  rivers  of  mod- 
erate size,  and  in  brooks, 
as  along  the  Mississippi  or 
Lower  Arkansas.  The  width 
of  the  swing  will  depend  on 
the  size  of  the  stream.  It 
may  be  a  few  rods  for  a  brook 
and  miles  for  a  great  river. 

40.  Meanders  sunk  in  a 
plateau.— Fig.  34  shows  how 
the  Caney  Fork  has  sunk  its 
channel  into  the  plateau 
country  in  eastern  Tennessee 
on  its  way  to  the  Cumberland.  Gaining  its  sinuous  course 
on  a  once  smooth  surface,  it  has  kept  it,  as  it  wears  its 
channel  down  toward  the  sea-level.  The  east  branch  of 
the  Susquehanna  Kiver  in  northern  Pennsylvania  and  the 
Osage  River  in  Missouri  show  the  same  conditions. 


Contour  Interval  100  feet 
Fig.  34.— Map  showing  bends  of  Caney 
Fork.  The  river  has  made  a  gorge 
300  to  400  feet  deep,  but  keeps  the 
bends  it  gained  as  a  meandering 
stream  on  the  plain  above. 


52      AN  INTRODUCTION   TO  PHYSICAL  GEOGRAPHY 


A  good  description  of  the  unstable  course  of  the  Missis- 
sippi is  found  in  Mark  Twain's  Life  on  the  Mississippi. 
The  author  describes  the  feelings  of  a  man  who  wakes  to 
find  that  the  river  has  changed  its  course  in  the  night  and 
transferred  his  plantation  from  Louisiana  to  Mississippi, 
and  vivid  emphasis  is  put  upon  the  difficulties  of  the  "  cub  " 
pilot  in  learning  the  river. 

We  have  yet  to  notice  a  most  important  result  of  these 
river  swings.  Their  development  not  only  varies  the  route 
of  the  water,  but  carries  it  sooner  or  later  to  all  parts  of 
the  valley  floor.  Coming  to  the  edge  of  the  flood-plain,  the 
river  cuts  a  slice  out  of  the  valley  slope,  now  on  this  side 
and  now  on  that,  and  thus  meandering  has  much  to  do  with 
making  narrow  valleys  grow  wide.  The  student  will  not 
need  to  search  long  to  find  lagoon  lakes,  abandoned  chan- 
nels, and  curved  blufls, 
cut  by  the  swinging 
stream  from  the  sides 
of  a  valley. 

41.  River  terraces. — 
We  have  seen  that  in 
each  flood  the  river 
spreads  a  film  of  mud 
over  its  flood-plain  and 
raises  its  surface.  At 
the  same  time  it  is  often 
sinking  its  bed.  Hence 
a  time  will  come  when 
flood- waters  will  not  rise 
on  the  flood-plain.  They 
will,  instead,  cut  into  its 
edges  and  trim  much  of  it  away,  and  out  of  this  waste  and 
that  brought  from  up-stream  will  form  a  new  flood-ground. 
The  remnants  of  the  higher,  forsaken  plain  are  known  as 
Eiver  or  Alluvial  Terraces.  Several  sets  of  them,  at  succes- 
sive levels,  are  seen  in  the  valley  of  the  Connecticut  and 


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Fig.  35.— Cross-profiles  of  a  valley  at  three 
stages  of  development,  to  show  how  river 
terraces  are  made,  r,  river,  a,  h,  c,  suc- 
cessive flood-plains,  a^,  h^,  remnants  of 
first  and  second  flood-plains,  remaining  as 
terraces. 


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54      AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

along  other  rivers.  They  are  not  often  important  in  size, 
but  may  afford  good  sites  for  single  homes  or  parts  of 
towns. 

42.  Deltas. — Gathering  its  tribute  of  land-waste  from  the 
Appalachian  and  Eocky  Mountains,  and  from  the  plateaus 


Fig.  S7.— Delta  formed  by  Chelan  "River  where  ft  enters  the  Colnmhin.  Note  the  dis- 
tributaries. The  white  area  Wii!>  overrun  by  a  recent  flood  which  deposited  much 
gravel  and  buried  all  vegetation. 

and  prairies  that  lie  between,  the  Mississippi  Eivcr  lays 
down  its  burden  on  the  plain  of  the  lower  valley  and  at  the 
borders  of  the  Gulf  of  Mexico.     Even  its  finest  mud  sinks 


TV 


RIVERS 


65 


to  the  bottom  as  the  flowing  river  unites  with  the  standing 
water  of  the  sea,  and  a  shoal  is  thus  built  up,  to  become  at 


Fig.  38.— Delta  of  the  Nile.  Note  the  fan-shape,  with  the  apex  at  Cairo.  The  dis- 
tributaries are  many.  Capes  are  built  into  the  sea  at  the  main  mouths.  There  are 
many  railways,  because  the  fertile  soil  supports  a  large  population. 

last  a  part  of  the  land.  So  the  river-plain  is  built  higher 
and  is  also  extended  southward.  The  growing  plain  is 
called  a  Delta.  The  river,  building  its  channel  above  the 
adjoining  land,  breaks  through  its  banks  at  various  points 
and  discharges  part  of  its  water  by  down-stream  branches. 
These  are  locally  called  Bayous,  but  are  more  widely  known 
as  Distributaries,  a  name  which  distinguishes  them  from  up- 
stream branches  or  tributaries.  Not  only  the  land,  but  the 
sea-bottom,  for  a  long  way  out,  belongs  properly  to  the 


56      AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

delta,  its  materials  having  come  down  the  river.  More 
than  1,000  feet  of  such  deposits  are  disclosed  by  an  artesian 
well  boring  at  Xew  Orleans.  Two  great  problems  are  al- 
ways presented  by  the  Mississippi  delta :  To  protect  the 
lands  from  flood,  wherefore  levees  are  made  at  great  ex- 
pense ;  and  to  keep  an  open  channel  for  navigation,  where- 
fore jetties,  or  artificial  banks,  have  been  built  along  one  of 
the "  passes  "  at  the  river-mouth,  to  confine  and  quicken 
the  flow,  and  thus  scour  and  deepen  the  channel. 

Other  deltas  must  be  more  briefly  described.  The 
Yukon  has  one  of  the  great  deltas  of  the  world,  giving 
off  its  first  distributary  100  miles  from  the  coast.  Its  delta 
is  a  Tundra,  or  plain  that  is  always  frozen  below,  though 
clothed  in  summer  with  grass  and  flowers  (see  page  155). 
The  delta  of  the  Colorado,  though  large,  is  not  so  evident 
on  a  map,  because  it  is  filling  the  head  of  the  Gulf  of  Cali- 
fornia rather  than  building  an  extension  in  the  open  sea. 
The  Xile,  the  Po,  the  Tiber,  and  the  Ehone  deltas  are 
notable  examples,  and  interesting  facts  about  them  should 
be  sought  in  encyclopedias  and  other  books  of  reference. 
The  Ganges,  Brahmaputra,  and  Hoang-Ho  are  enormous 
deltas  of  the  Asiatic  sea-border. 

43.  Deltas  on  lake  borders. — It  must  not  be  thought 
that  all  deltas  contain  hundreds  or  thousands  of  square 


FiQ.  39.— Section  of  a  delta  made  of  gravel  and  sand. 

miles  or  are  built  on  the  borders  of  the  ocean.  Many  are 
seen  on  the  shores  of  lakes,  and  when  a  swift  upland  stream 
is  there  suddenly  checked  the  delta  will  contain  sand, 
gravel,  and  boulders,  and  thus  be  different  from  the  ma- 


RIVERS  67 

rine  delta.  Its  form  will  be  different  also,  and  instead  of 
the  delta  surface  passing  smoothly  down  to  the  bottom  of 
the  water,  it  will  have  an  abrupt  slope  in  front.  When  the 
stream,  pushing  for  a  little  way  through  the  shallow  water, 


Fig.  40 — Miniature  delta.  During  a  rain  a  pool  was  formed  at  the  foot  of  a  steep 
slope  of  earth.  A  rill  dug  a  miniature  gorge  in  the  slope  and  washed  the  waste  to 
the  pool,  where  it  built  a  delta.  Before  the  pool  dried  away  the  wind  made  wave- 
lets, which  carved  a  shore  terrace  about  the  edge  of  the  delta. 

reaches  the  brink,  its  load  will  settle  and  slide  down  the 
incline,  much  as  teams  and  wagons  make  a  "  fill "  in  carry- 
ing a  road  grade  across  a  gorge.  The  interior  structure,  if 
we  should  slice  the  delta  through,  would  appear  as  in  Fig. 
39.  The  stream  will  swing  from  one  line  to  another, 
building  up  the  delta  on  different  parts  of  its  front,  and 
shaping  that  front  into  a  series  of  lobes.  All  of  these  fea- 
tures can  be  seen  in  miniature  after  a  wayside  pool,  receiv- 
ing a  wet-weather  torrent,  has  dried  away  (Fig.  40). 

44.  Young,  mature,  and  old  valleys. — These  are  impor- 
tant terms  in  physical  geography,  and  we  are  now  prepared 


58       AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

to  understand  them.  They  are  useful  because  they  express 
the  great  fact  that  the  forms  of  the  land  are  changing,  or 
having  a  development  which  can  be  traced,  somewhat  as 
we  follow  the  growth  of  a  plant  or  the  history  of  a  town. 
They  are  used,  as  we  shall  see,  not  only  of  valleys,  but  of 
other  land  forms,  as  plateaus  or  mountains. 

A  young  valley  is  narrow,  has  steep  sides,  and  carries  a 
vigorous  stream  flowing  on  an  uneven  floor.  The  gorges 
already  named  are  illustrations.  A  mature  valley  is  deep, 
but  open  also,  having  flaring  sides,  and  gentle,  rounded 
upper  slopes.  The  valley  of  Seneca  Lake  is  mature,  but 
Watkins  Glen,  entering  it,  is  young.  The  one  was  a  river 
valley  growing  deeper  and  wider  long  before  the  Ice  Age, 
while  the  other  has  been  made  since  the  glaciers  disap- 
peared. All  the  great  valleys  of  New  York  and  Pennsyl- 
vania are  mature.  The  Shenandoah  of  Virginia  and  the 
Connecticut  Valley  in  Massachusetts  illustrate  a  similar 
degree  of  growth. 

The  Hudson  Valley  from  Glens  Falls  to  K'ewburg  is  12 
to  20  miles  wide  and  is  fully  mature.  Through  the  High- 
lands it  is  narrow  and  steep-walled,  and  we  call  it  young. 
Here  the  case  is  different,  however,  for  one  part  of  the  val- 
ley is  perhaps  as  old  in  time  as  the  other.  The  open  part 
is  cut  in  the  soft  rocks,  which  crumble  readily  away.  The 
Highland  gorge  is  cut  in  hard  rocks,  and  the  river's  task, 
being  slowly  done,  is  less  advanced.  The  gorge  of  the 
Mohawk  at  Little  Falls,  X.  Y.,  is  both  younger  in  time  and 
is  cut  in  harder  rocks,  while  the  wide  parts  of  the  valley,  as 
at  Utica  or  Amsterdam,  are  in  soft  rocks  and  are  older. 
But  this  can  not  be  fully  explained  here.  The  develop- 
ment of  a  valley  depends  thus  on  the  time  for  wear  and 
the  hardness  or  resistance  of  the  rocks. 

We  have  already  seen  how  a  narrow  valley  grows  wide 
and  a  steep-walled  valley  becomes  open.  The  floor  of  the 
valley  is  widened  by  the  swing  of  the  river  in  gentle  curves 
or  strong  meanders,  while  the  slopes  are  reduced  by  all  the 


Pio.  41.— Map  of  part  of  West  Virginia.  Scale,  1  inch  =  2  miles.  Contour  interval, 
100  feet.  The  streams  have  full  possession  of  the  land  ;  their  gorges  penetrate  all 
parts  of  the  plateau.  Roads  find  better  grades  along  the  valleys  than  on  the 
uneven  divides.    See  Sec.  45. 


RIVERS  59 

processes  of  decay  or  weathering,  as  described  in  the  next 
chapter.  At  the  same  time  rapids  and  falls  disappear  and 
the  river  comes  to  flow  on  a  graded  floor. 

As  the  slopes  fade  out,  the  valleys  become  wide,  the 
divides  low,  and  the  rivers  sluggish,  and  the  whole  land  sur- 
face passes  into  old  age.  The  student  should  try  to  imag- 
ine the  evolution  of  a  valley  from  early  youth  through  the 
various  stages  of  maturity  to  old  age. 

45.  The  general  work  of  a  river  system. — Let  us  picture 
to  ourselves  an  elevated  plain  near  the  sea,  and  a  branch- 
ing river  system  formed  upon  it.  Where  the  river  descends 
steeply  to  the  sea  it  will  plow  a  gorge.  This  gorge  will 
extend  backward,  up-stream,  branching  where  the  river 
branches,  and  its  divisions  will  in  time  ramify  throughout 
the  river  basin.  While  they  are  growing  at  the  head- 
waters, the  lower  gorge  will  be  changed  to  an  open  valley, 
and  this  broadening  also  will  extend  gradually  up-stream. 
At  flrst  there  will  be  remnants  of  plain  between  the  gorges, 
but  these  will  grow  narrow  as  the  gorges  grow  broad,  and 
will  finally  be  replaced  by  crested  hills,  which  will  then 
soften  and  sink  with  the  flattening  of  valley  slopes.  All 
these  changes  will  proceed  from  the  trunk  stream  toward 
the  confines  of  the  basin  and  at  last  reach  the  outer  divides 
separating  the  basin  from  other  basins.  Thus  the  whole 
plain  will  be  at  first  furrowed  and  made  rough,  and  the 
ridges  between  furrows  will  be  afterward  reduced  so  as  to 
lessen  the  roughness.  In  a  very  long  time  the  entire  basin 
will  be  again  made  a  plain,  but  the  final  plain  will  be  much 
lower  than  the  original,  being  but  little  above  the  level  of 
the  sea. 

The  great  fact  is,  that  the  level  of  the  land  is  slowly 
reduced  and  the  waste  is  carried  off  to  the  sea-bottom. 
The  uplands  of  New  England,  or  Virginia,  are  now  of  mod- 
erate height.  They  were  probably  once  much  higher. 
The  Highlands  of  Scotland  are  subdued  lands.  They  may 
have  towered  like  the  Alps  or  Andes.     Follow  the  river 


60       AN   INTRODUCTION  TO  PHYSICAL   GEOGRAPHY 

from  the  mountains  to  the  sea.  See  the  waste  in  talus  and 
fan,  terrace,  flood-plain,  and  delta.  But  much  of  it  has 
gone  beyond  the  shore-line,  and  spreads  far  out  to  sea. 
We  shall  come  to  it  again  in  our  study  of  the  ocean. 

46.  Imperfect  development  of  drainage. — If  the  farmer 
has  a  swampy  field,  he  opens  a  channel  or  a  network  of 
ditches  and  draws  the  surplus  water  away.  He  may  even 
cut  across  a  rim  of  higher  ground  if  the  cost  be  not  too 
great.  If  human  life  were  longer  and  he  could  afford  to 
wait,  nature  would  drain  the  swamp  or  pond  for  him. 
Some  stream  would  head  into  it  and  carry  away  the  waters. 
So,  wherever  we  see  water  standing  on  the  land  in  lake  or 
swamp,  we  must  understand  that  the  drainage  is  still  im- 
perfect, that  the  river  system  has  not  yet  developed  its 
branches  in  a  mature  way  and  taken  possession. 

47.  Lakes. — These  are  illustrations  of  imperfect  drain- 
age, and  if  many  are  present  they  stamp  a  region  as  having 
a  young  surface.  Lake  basins  are  depressions  which  detain 
the  waters  from  passing  directly  to  the  sea.  They  are 
made  in  many  ways  which  can  not  be  fully  described  in  an 
elementary  book.  The  greater  number  are  due  to  the 
glacial  invasion  and  will  be  explained  in  a  later  chapter. 
Some,  like  Great  Salt  Lake  and  the  Dead  Sea,  are  due  to 
bendings  or  unequal  movements  of  the  earth's  crust.  Small 
lakes  sometimes  occupy  old  volcanic  craters  (Fig.  147). 
Others  lie  in  sink  holes  (Fig.  71),  in  regions  of  great  cav- 
erns and  the  caving  in  of  the  surface  rocks.  Such  lakes  are 
common  in  Kentucky.  We  have  seen  how  cut-offs  in  river 
valleys  form  ox-bow  lakes.  When  we  study  the  shores  of 
the  sea,  we  shall  observe  the  making  of  lakes  by  shutting 
off  the  waters  of  deep  bays.  Alluvial  cones  at  the  mouths 
of  some  Swiss  gorges  are  built  across  the  main  valleys, 
crowd  the  streams  to  the  other  side,  and  dam  the  waters 
coming  from  above.  Landslips  and  lava  floods  blockade 
valleys  into  which  they  descend  and  make  small  lakes  be- 
hind them. 


Fig.  42.— Head  of  Seneca  Lake,  New  York.  Scale,  1  inch  =  1  mile.  Contour  interval, 
20  feet.  Catharine  and  Watkins  Creeks  are  bringing  waste  to  fill  the  lake,  and 
have  already  built  the  alluvial  plain  from  Montour  falls  to  Watkins. 


RIVERS 


61 


48.  Disappearance  of  lakes. — But  we  are  here  most  con- 
cerned to  see  how  lakes  disappear  as  drainage  becomes 
mature.  If  the  rapids  of  the  St.  Lawrence  and  the  rocks 
of  the  Thousand  Islands  should  be  cut  away,  Lake  Ontario 
would  be  partly  drained,  but  only  in  part,  because  about 
400  feet  of  its  depth  are  below  sea-level.  But  when  Niagara 
has  finished  its  work  the  bed  of  Lake  Erie  will  be  dry,  for 
its  lowest  point  is  more  than  100  feet  above  the  surface  of 
Lake  Ontario.  This  would  take  a  long  time,  but  the  process 
is  already  complete  with  many  small  lakes,  which  once  ex- 
isted, but  whose  bottoms  are  now  meadows. 

This  brings  us  to  the  second  important  way  in  which 
lakes  disappear.  Streams  bring  down  their  load  and  build 
deltas  at  the  edge  and  spread  the  mud  over  the  entire  bot- 
tom. Water-loving  plants  grow  about  the  edges  and  help  to 
fill  the  shallow  places.  Small  shell-making  creatures  abound 
in  some  lakes,  and  their  crumbling  remains  form  a  white  de- 
posit of  calcium  carbonate  or  shell  marl.  Trees  and  leaves 
add  their  part,  and  at  length  the  basin  is  full  and  the  water 
is  displaced.  The  sawing  of  outlet  channels  and  the  filling 
of  basins  are  responsible  for 
the  disappearance  of  many 
lakes,  and  all  stages  of  the 
process  can  be  found  by  the 
observing  student  in  the 
northern  United  States. 

The  vlies,  or  flat  mead- 
ows of  the  Adirondack  region 
in  New  York,  represent  filled 
lakes.  Ithaca,  N.  Y.,  lies 
upon  a  broad  delta  formed  at 
the  head  of  Cayuga  Lake,  of 
waste  brought  in  by  several 
streams.  Watkins  occupies 
a  similar  delta  at  the  head  of  Seneca  Lake  (Fig.  42).  A 
delta  is  rapidly  encroaching  on  Lake  St.  Clair  (Fig.  43). 


LAKE  STCj 


Fig.  43.— Delta  of  the  St.  Clair  River. 
Scale,  1  inch  =  11  miles. 


62      AN  INTRODUCTION   TO  PHYSICAL  GEOGRAPHY 

The  south  end  of  Lake  Lucerne  in  Switzerland  is  diminish- 
ing by  the  growth  of  a  delta  on  which  Fliielen  and  Altdorf 
stand.  A  similar  shortening  occurs  where  the  Rhine  enters 
Lake  Constance  and  the  Rhone,  Lake  Geneva. 

49.  Swamps. — All  marsh  lands  are  marks  of  imperfect 
drainage,  and  they  often  are  due  to  the  nearly  completed 
filling  of  lakes.  Others  occur  on  flood-plains  and  deltas, 
and  are  due  to  wanderings  and  irregular  deposits  of  streams. 
Swamps  are  often  caused  by  checking  of  waterflow  through 
the  growth  of  trees  and  shrubs,  and  they  disappear  when 
forests  are  cut  away.  Swamps  caused  by  the  dams  which 
beavers  construct  (Fig.  234)  have  a  similar  history. 

50.  Imperfect  drainage  on  new  lands. — Much  of  the  flat 
ground  along  our  Atlantic  coast  was  formerly  a  part  of  the 
sea-bottom,  and  has  been  turned  into  land  by  the  gentle 
rising  of  the  continent.  The  streams  have  not  had  time  to 
cover  the  surface  with  their  head- waters.  Hence  the  rain 
falling  on  the  smooth  areas  between  the  streams  evaporates, 
or  drains  off  slowly  underground.  The  same  is  true  of  the 
plains  drained  by  the  Maumee  and  the  Red  River  of  the 
North,  except  that  these  formed  the  beds  of  lakes  and  be- 
came land  by  the  draining  off  of  the  waters.  Compare  the 
fully  drained  land  of  Fig.  41  with  the  scattered  streams  and 
smooth  interstream  surfaces  of  Fig.  44. 

51.  Arrangement  of  streams  depending  on  the  form  of  the 
rocks. — In  northwestern  Pennsylvania  the  rivers  branch 
more  and  more  as  one  goes  toward  the  head- waters,  just  as 
boughs  and  twigs  branch  from  the  main  limbs  of  a  tree. 
The  rocks  there  lie  in  nearly  horizontal  beds,  and  do  not 
influence  the  ground  plan  of  the  streams.  But  in  central 
Pennsylvania,  where  the  beds  are  tilted  and  the  country  is 
traversed  by  alternating  belts  of  strong  and  weak  rocks,  the 
arrangement  of  streams  is  different.  Valleys  have  been 
opened  in  the  belts  of  weak  rocks,  leaving  the  strong  rocks 
prominent  as  mountain  ridges.  A  few  large  trunk  streams, 
like  the  Susquehanna  and  Lehigh  Rivers,  cross  or  cut  through 


Fig.  44— Part  of  Virginia,  bordering  the  Potomac  River.  Scale,  1  inch  =  1  mile. 
Contour  interval,  20  feet.  Streams  are  developing  their  valleys  by  eating  back- 
ward into  the  land,  but  tracts  of  the  original  plain  remain.  Roads  find  easy  grades 
on  the  divides.     See  Sec.  50. 


RIVEES 


63 


the  ridges  without  swerving,  but  most  streams  run  parallel 
to  them,  following  the  belts  of  weak  rock.  It  is  common 
for  a  small  stream  flowing  along  a  valley  between  two 
ridges  to  turn  and  pass  by  a  "  water-gap  "  through  one  of 
them.     If  a  sketch  map  of  the  drainage  be  traced,  to  avoid 


Fig.  45.— Delaware  Water-Gap.  A  long  mountain  ridge  is  here  divided  from  top  to 
base  by  a  notch,  through  which  the  Delaware  River  flows.  Had  not  the  river 
sawed  out  this  notch,  the  mountain  would  continue,  with  even  height,  across  the 
view. 

the  confusion  of  other  natural  or  political  features  of  a  map, 
the  streams  will  form  a  network  of  rude  right  angles,  and 
hence  such  drainage  is  often  called  Eectangular  or  Trel- 
lised,  from  its  close  resemblance  to  a  grape-vine  trained  in 
that  manner.  The  student  should  contrast  the  tree-pattern 
and  trellis-pattern  of  drainage  as  seen  in  Figs.  46  and  47. 

52.  Drainage  modified  by  rising  and  sinking  of  the  lands. 
— It  is  well  known  that  lands  are  sometimes  higher  and 
sometimes  lower  in  relation  to  sea-level.  Thus  the  geolo- 
gists of  ]N"ew  Jersey  have  found  stumps  of  trees  submerged 
in  sea-water.  Corduroy  roads  made  in  early  days  have  also 
been  covered,  and  the  salt  water  comes  farther  into  the 
mouths  of  streams  than  in  former  years.  They  have  there- 
fore concluded  that  the  coast  is  slowly  sinking;  the  rate 
6 


64       AN  INTRODUCTION  TO   PHYSICAL   GEOGRAPHY 


is  about  two  feet  in  100  years.  There  is  another  proof  that 
the  Atlantic  coastal  region  has  gone  down.  If  the  student 
will  look  at  the  map  of  Chesapeake  Bay  (Fig.  47)  he  will 
see  that  its  ground-plan  comprises  a  trunk  with  numerous 
branches.  It  is  like  a  river  system,  except  that  trunk  and 
branches  are  comparatively  stout.  If  we  imagine  a  stream 
system  carving  valleys  at  the  sea-border,  and  then  picture 
the  sea-border  as  sinking  so  that  the  salt  waters  flow  into 
the  main  valley  and  its  tributaries,  we  shall  get  such  a  plan 
as  Chesapeake  Bay  shows.  This  is  the  real  history  of  the 
region.     When  the  land  stood  higher  the   Susquehanna 

Eiver  flowed  to  the  edge 
of  the  ocean,  and  the  Po- 
tomac and  James  were 
its  branches.  When  the 
sinking  of  the  laud  ad- 
mitted the  waters  of  the 
ocean  the  rivers  all  be- 
came tributary  to  Chesa- 
peake Bay.  Delaware 
Bay  and  Albemarle  and 
Pamlico  Sounds  have 
the  same  origin.  Geog- 
raphers often  speak  of 
the  "  drowning  "  of  river 
valleys  by  subsidence. 

If,  on  the  other  hand, 
the  land  were  to  rise  out 
of  the  sea,  the  edge  of 
the  sea -bed  would  be 
added  to  the  land,  and 
the  rivers  would  flow 
out  across  the  new  land 
to  the  receding  sea-bor- 
rivers  would  have  to  de- 
scend more  to  reach  the  sea.     By  reason  of  this  greater 


Fig.  46.— Trellised  drainage  in  central  Pennsyl- 
vania. The  conrse  of  the  Susquehanna  is 
independent  of  mountain  ridges;  other 
streams  conform  to  them.  Southeast  of  the 
ridges  the  rocks  are  less  varied  and  the 
stream  pattern  is  tree-like. 

der.     As  the  land  came  up,  the 


RIVERS 


65 


descent  they  would  flow  faster,  and  begin  to  cut  narrow 
channels  again,  where  they  had  perhaps  wandered  over 
their  deltas  and  swamp  lands. 


Fig.  47.— Coastal  region  from  New  Jersey  to  North  Carolina.  Scale,  1  inch  =  110 
miles.  The  heavy  line  represents  the  Fall  Line  (Sec.  59).  The  bays  are  drowned 
valleys  (Sec.  52).  Along  the  belt  of  the  Appalachian  Mountains  the  stream 
pattern  is  trellised  (Sec.  51),  elsewhere  tree-like. 

53.  Shifting  of  divides. — One  of  the  more  simple  cases 
can  best  be  explained  by  the  diagram,  Fig.  48.  Let  ABC 
represent  the  profile  of  a  region  whose  water-parting  is  at 
B^  and  which  has  a  short  steep  slope  A  5,  and  a  long  gen- 


Q6       AN   INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

tie  slope  BC.  It  is  clear  that  the  streams  coursing  down 
AB  will  be  more  swift  and  destructive  than  those  flowing 
from  B  to  C.     The  land  waste  will  be  largely  carried  to  A, 

B 


A 

Fig.  48.— Cross-profile  of  a  divide,  showing  changes  in  height  and  position. 

and  the  divide  will  move  to  B'  and  then  to  B".  It  will  not 
stop  until  the  slopes  on  its  two  sides  arc  the  same,  but  its 
shifting  will  be  slow  toward  the  last. 

From  near  the  east  front  of  the  Catskill  Plateau 
Schoharie  Creek  flows  northwest,  then  north,  then  east  by 
the  Mohawk  to  tide-water  in  the  Hudson  at  Troy.  Its 
broad,  flat,  upper  valley  is  seen  in  the  north  part  of  the 
map  on  page  14.  But  the  east-flowing  streams  on  the  Cats- 
kill  front  reach  tide-level  in  the  Hudson  in  a  few  miles. 
They  are  therefore  swift  and  vigorous,  and  they  are  cutting 
back  great  gorges  and  robbing  territory  from  the  Schoharie. 
In  the  same  way  the  southern  branches  of  the  Mohawk  are 
conquering  land  from  the  Susquehanna  basin  in  central 
Xew  York. 

54.  River  systems. — The  rest  of  this  chapter  will  be 
given  to  a  short  review  of  the  more  important  rivers  of 
North  America.  Bringing  from  his  school-work  in  geogra- 
phy a  good  knowledge  of  their  directions,  relative  strength, 
and  the  extent  of  their  basins,  the  student  should  now 
comprehend  more  fully  their  character.  The  divides  should 
be  traced  and  their  character  observed  with  all  the  helps 
obtainable,  and  careful  study  should  be  given  to  the  drain- 
age basin  in  which  one  lives. 

55.  The  Mississippi  system. — This  single  system  well 
studied  will  give  a  nearly  complete  introduction  to  physi- 
cal geography.  Here  we  have  the  drainage  of  the  central 
United  States  from  the  Appalachian  to  the  Eocky  Moun- 
tains.    A  relatively  narrow  belt  on  the  north  is  tributary 


RIVERS  67 

to  the  Great  Lakes,  and  a  similar  small  strip  on  the  south 
drains  to  the  Gulf  by  other  streams.  The  source  of  the 
river  is  1,680  feet  above  the  sea,  and  it  is  fed  by  many 
lakes.  These  are  of  glacial  origin,  and  all  the  upper  part 
of  the  basin  lies  within  the  area  modified  by  the  great  ice 
sheet.  The  upper  river  flows  among  hills  of  glacial  waste, 
usually  in  an  open  valley.  At  Minneapolis  it  enters  a 
short  gorge,  where  the  old  valley  for  a  few  miles  was  shut 
off  by  a  mass  of  glacial  waste,  and  the  river  forced  to  carve 
a  new  valley  in  the  rocks.  At  some  points  on  the  borders 
of  Iowa  the  valley  is  narrow,  as  if  the  same  thing  had  hap- 
pened there.  The  bluffs  of  the  lower  river,  from  the 
mouth  of  the  Ohio,  are  cut  in  soft  material,  and  give  sites 
to  such  cities  as  Memphis,  Xatchez,  and  Vicksburg.  The 
flood-plain  is  from  5  to  80  miles  wide.  Its  broader  and 
lower  part  is  properly  part  of  the  delta,  for  a  deep  bay  once 
reached  up  from  the  Gulf  to  the  point  where  the  Ohio  now 
comes  in,  and  this  bay  has  gradually  been  filled  by  the 
waste  the  river  has  brought. 

The  Missouri  is  so  much  larger  than  the  upper  Missis- 
sippi that  it  might  well  be  considered  as  the  trunk  stream. 
Here  we  find  the  torrent  head-waters  in  the  Eocky  Moun- 
tains in  Montana  and  Wyoming,  followed  by  a  long  and 
comparatively  quiet  course  across  the  Great  Plains,  where 
the  waters  are  heavy  with  waste,  and  can  sink  their  valley 
but  little  below  the  general  surface.  The  Platte  River 
in  Nebraska  is  noted  for  its  great  width  and  shallow- 
ness. The  next  great  tributary  is  the  Arkansas.  This 
river  has  its  torrential  course  in  central  Colorado,  an  open 
valley  south  from  Leadville  between  mountain  ranges,  a 
deep  transverse  passage  eastward  by  the  Royal  Gorge,  and 
then  resembles  the  Missouri  in  its  long  passage  across  the 
plains.  In  eastern  Arkansas  its  flood-plains  and  cut-off 
lakes  are  like  those  of  the  lower  Mississippi  (Fig.  32). 
The  Red  River  can  only  be  named,  and  we  pass  to  the  east- 
ern affluents.    The  Illinois  River  has  cut  a  shallow  valley 


Fio.  49.— The  rivers  of  North  America. 


68 


RIVERS  69 

across  the  prairies  and  is  interesting  as  having  once  carried 
much  of  the  outflow  from  the  Great  Lakes  region.  The 
channel  thus  made,  more  than  a  mile  broad,  is  seen  in  Fig. 
11  as  a  valley  between  high  bluffs,  containing  the  mod- 
ern flood-plain.  The  Ohio  brings  the  waters  from  western 
Pennsylvania,  from  southwestern  Xew  York  within  eight 
miles  of  Lake  Erie,  from  far-away  Virginia  through  the 
Kanawha,  and  from  western  North  Carolina  by  the  curi- 
ously winding  channel  of  the  Tennessee. 

The  Mississippi  is  a  continental  river,-  with  its  myriad 
torrents  in  the  mountains  of  east  and  west,  its  leisurely 
stretches  across  broad  plateaus  and  plains  on  either  hand, 
to  the  trunk  channel,  down  which  the  ceaseless  stream  of 
water  and  land-waste  pours  into  the  Gulf. 

56.  St.  Lawrence  system. — It  is  useful  to  regard  all  of 
the  Great  Lakes  as  expansions  of  the  St.  Lawrence  Eiver. 
A  great  river  system  drained  eastward  over  this  region  be- 
fore the  lakes  were  in  existence.  Portions  of  its  valleys 
were  deepened  by  the  ice,  and  other  portions  were  block- 
aded by  rock-waste,  and  so  the  lakes  came  into  being.  In 
this  view,  the  St.  Louis  Eiver  of  Minnesota,  the  Sault  St. 
Marie,  the  St.  Clair,  Detroit,  and  Niagara,  and  each  great 
lake,  are  but  different  parts  of  the  one  great  river.  The 
river  descends  but  21  feet  from  the  Superior  to  the  Huron 
level,  thence  8  feet  to  the  Erie  level,  and  326  feet  by  Niag- 
ara Eiver  and  Falls  to  Ontario.  The  gentle  reaches  and 
rapids  below  the  Thousand  Islands  bring  the  river  to  tide- 
level  at  Montreal.  Thence  the  St.  Lawrence  valley  is  occu- 
pied by  an  inlet  of  the  sea. 

This  is  commercially  the  most  important  inland  water 
system  of  the  world.  Here  are  the  ports  of  Duluth,  Mil- 
waukee, Chicago,  Detroit,  Cleveland,  Buffalo,  Montreal,  and 
Quebec.  The  greater  of  these  ports  vie  with  New  York, 
Liverpool,  and  Hamburg  in  the  tonnage  of  their  shipping. 
Over  this  route  pass  the  iron  ore  of  Minnesota,  and  the 
wheat  and  corn  of  the  prairies  and  the  plains.     Such  a 


70       AN  INTRODUCTION  TO   PHYSICAL   GEOGRAPHY 

body  of  waters  penetrating  the  heart  of  Xorth  America 
ma}^  be  compared,  in  its  influence  on  the  development  of 
commerce  and  the  shaping  of  history,  to  the  English  Chan- 
nel and  the  North  and  Baltic  Seas. 

57.  Drainage  of  New  England.— The  Penobscot  and  Ken- 
nebec, the  Merrimac,  Connecticut  and  Housatonic,  all  trav- 
erse the  worn  mountain  and  plateau  region  of  northern 
and  central  New  England,  and  reach  the  sea  at  the  heads 
of  narrow  bays,  which  bear  witness,  like  those  of  the  St. 
Lawrence  and  Chesapeake,  to  the  former  elevation  of  the 
land  and  its  later  sinking.  All  of  these  rivers  are  actively 
deepening  their  upper  courses,  and  many  of  them  show 
fine  terraces  and  flood-plains.  The  Connecticut  has  an 
open  valley,  carved  out  of  soft  rocks,  from  northern  Massa- 
chusetts to  Middletown,  Conn. 

58.  Rivers  of  New  York. — Though  not  a  lofty  upland, 
New  York  is  remarkable  for  the  wide  dispersion  of  its 
waters,  which  flow  to  the  Gulfs  of  St.  Lawrence  and  Mexico, 
and  to  Chesapeake  and  Delaware  Bays.  Its  chief  internal 
river,  the  Hudson,  is  tidal  for  150  miles,  and  has  had  much 
to  do  in  determining  the  lines  followed  by  early  settlement 
and  by  later  travel  and  commerce. 

59.  Rivers  of  the  Southern  Atlantic  slope. — These  rise  in 
the  Alleghany  Plateau,  as  the  Susquehanna  and  the  Poto- 
mac, or  in  the  Appalachian  Mountain  belt,  as  the  Lehigh 
and  Schuylkill.  Still  farther  south  the  rivers  rise  in  the 
mountains,  traverse  the  low,  worn  Piedmont  Plain,  cross 
the  "  Fall  Line,"  and  run  along  tidal  courses  between 
flat  grounds  to  the  sea.  The  Fall  Line  is  the  boundary 
between  an  inner  belt  of  older,  harder  rocks  of  higher  sur- 
face, and  the  soft,  low-lying  rocks  of  the  Atlantic  Coastal 
Plain.  The  crossing  is  often  marked  by  rapids,  locating 
the  head  of  navigation,  affording  water-power,  and  deter- 
mining the  sites  of  cities  (Fig.  47). 

60.  The  Colorado  River. — This  great  stream  drains  much 
of  Wyoming,  Colorado,  New  Mexico,  and  Utah,  and  nearly 


RIVERS  71 

all  of  Arizona.  Its  northern  and  northeastern  branches  head 
among  mountains  and  course  through  gorges  and  high  val- 
leys. Its  trunk  first  crosses  a  system  of  uplifted  plateaus, 
through  which  it  has  excavated  a  series  of  profound  canyons, 
and  then  traverses  lowlands  to  the  Gulf  of  California.  The 
descent  is  great,  being  6,000  feet  from  Green  River  City, 
Wyo.,  to  the  sea,  while  the  Ohio-Mississippi  in  flowing 
from  Pittsburg  to  the  Gulf  of  Mexico,  a  greater  distance, 
descends  but  700  feet.  The  Grand  Canyon,  celebrated  not 
only  for  its  scenery,  but  as  the  most  impressive  of  all  exam- 
ples of  the  work  of. rivers  in  making  gorges,  is  at  one  point 
more  than  a  mile  in  depth.  Its  lower  part  is  there  narrow 
and  steep-walled,  but  above  it  opens  widely,  being  elabo- 

'76 


if%^^S?^^i|^!'^'S'^  3  2  }^i'''iS\!^'iV'^'vi7^^^^ 


Fig.  50.— Cross-profile  of  the  Grand  Canyon  of  the  Colorado  River.  Base-line  repre- 
sents sea-level.  1,  granite  ;  2,  5,  and  7,  sandstone  ;  U  and  8,  limestone  ;  3  and  6, 
shale.  Scale,  1  inch  =  15,000  feet.  Compare  with  frontispiece  and  Fig.  64.  The 
frontispiece  represents  the  inner  gorge  (i)  and  terrace  (2),  with  the  middle  cliff  (5) 
at  left,  and  the  upper  cliff  (8)  in  the  distance.  Fig.  64  shows  the  upper  and  middle 
cliffs. 

rately  carved  in  alcoves,  buttresses,  and  turrets  (see  the 
frontispiece  and  Fig.  64).  The  hard  beds  make  conspicu- 
ous cliffs,  and  the  soft  beds  are  obscured  by  slopes  of  waste. 
The  secret  of  the  topography  is  in  the  dryness  of  the  region 
and  the  vigor  of  the  river.  The  general  surface  decays 
slowly,  while  the  stream,  fed  with  mountain  rains  and 
snows,  and  flowing  rapidly,  cuts  into  the  rocks  like  a  sharp 
steel  saw. 

61.  Drainage  of  California. — At  the  east  is  a  high  moun- 
tain range,  the  Sierra  Nevada.  The  Coast  Range  folloAvs 
the  ocean.  Between  the  two  is  a  long,  wide,  central  valley 
drained  southward  by  the  Sacramento  and  northward  by 
the  San  Joaquin.  These  rivers  gather  the  torrent  waters 
from  both  ranges  of  mountains,  and  come  together  at  the 


72       AN  INTRODUCTION  TO  PHYSICAL   GEOGRAPHY 

head  of  a  narrow  bay  connected  with  the  Pacific  by  the 
Golden  Gate.  The  mountains  offer  mineral  wealth,  and 
the  streams  have  not  only  washed  out  the  gold  dust,  but 
have  formed  the  soil  and  'furnish  the  water  for  the  rich 
agriculture  of  the  great  valley. 

62.  Columbia  River. — This  stream  heads  on  the  western 
slopes  of  the  Rocky  Mountains  and  cuts  across  or  through 
the  Cascade  Range  by  wild  defiles.     It  receives  as  its  chief 


Fig.  51.— Canyon  of  Snake  Rives,  in  Idaho. 


tributary  the  Snake  River.  Over  much  of  the  valley  of 
the  Snake  broad  and  deep  floods  of  lava  were  poured  in 
earlier  times.  Through  these  the  river  has  carved  a  deep 
and  very  long  gorge,  which  is  only  second  in  rank  to  the 
Grand  Canyon  of  the  Colorado.  The  Columbia  River  is 
affected  by  the  tides  to  a  distance  of  140  miles  from  its 
mouth. 

63.  The  Yukon. — In  passing  the  Fraser,  the  Mackenzie, 
and  the  rivers  of  the  Hudson  Bay  region  with  a  bare  men- 
tion, the  student  should  not  forget  that  they  are  important 
streams ;  but  we  turn  now  to  the  great  Alaskan  river.     The 


RIVERS  Y3 

Yukon  is  2,000  miles  long,  and  has  a  basin  about  one-third 
as  large  as  that  of  the  Mississippi.  It  is  the  artery  of  the 
great  interior  plains  of  Alaska,  is  navigable  for  1,500  miles, 
and  is  therefore  of  great  importance  as  a  route  of  travel 
and  commerce,  despite  the  fact  that  it  is  closed  by  ice  for 
more  than  half  the  year.  As  we  have  seen,  it  has  built 
into  Bering  S^a  a  great  delta. 


CHAPTEE  IV 

WEATHERING    AND    SOILS 

In"  our  study  of  streams  we  have  seen  that  flowing  water 
does  not  act  alone  in  breaking  up  the  rocks  and  changing 
the  face  of  the  earth.  We  now  seek  to  understand  that 
many  forces  work  together  to  cause  a  wasting  of  the  land 
surface.  As  all  this  work  is  done  upon  the  rocks,  we  must 
study  a  few  kinds  of  rock  in  order  to  see  the  nature  of 
these  changes. 

64.  Sandstone. — If  we  crush  a  piece  of  common  sandstone 
and  examine  the  fragments  with  a  hand  magnifier,  we  shall 
find  them  to  be  grains  of  sand  similar  to  those  we  see  in  a 
sand-bank  or  on  the  beach.  Commonly  the  grains  consist 
largely  of  quartz,  a  mineral  resembling  glass,  but  much 
harder.  Other  mineral  fragments  occur,  especially  feld- 
spar, but  quartz  is  the  more  abundant.  Upon  the  grains, 
if  the  stone  is  red,  may  be  seen  bits  or  patches  of  reddish 
substance.  This  is  an  oxid  of  iron  and  is  the  cement 
which  held  the  grains  together.  Other  substances,  like 
calcium  carbonate,  may  serve  as  a  cement.  This  means 
that  all  sandstones  once  consisted  of  loose  sand-grains  which 
have  been  bound  together  by  a  cement. 

If  the  student  will  search  in  a  boulder  heap,  he  will 
probably  find  some  piece  of  sandstone  which  is  so  soft 
that  it  can  be  cut  with  a  knife,  or  will  even  crumble  in  the 
hand.  Here  the  cement  is  losing  its  hold,  and  the  sand 
is  going  back  to  its  old  condition.  Let  us  weigh  a  piece 
of  dry  sandstone,  then  soak  it  a  day  in  water  and  weigh 
it  again.  We  shall  find  that  water  has  been  absorbed, 
74 


WEATHERING  AND  SOILS  Y5 

sometimes  as  much  as  one-eighth  of  the  weight  of  the 
stone.  This  means  that  there  is  free  space  among  the 
sand-grains,  which  water  or  air  may  enter.  Suppose  the 
stone  freezes  after  absorbing  the  water.  Expansion  will 
take  place  and  the  sand-grains  will  tend  to  be  thrust  apart, 
and  after  many  such  wettings   and  freezings,  the  stone 


Pio.  5a.— Watkins  Gleu  ;  a  gorge  carved  from  beds  of  shale. 

will  crumble.  Hence  a  very  porous  sandstone  is  not  a 
good  building  stone  for  outside  work.  A  little  search  will 
discover  sandstones,  in  buildings  or  other  structures,  which 
show  scaling.  This  is  one  of  the  ways  in  which  the  stone 
can  be  destroyed,  but  the  fact  most  important  to  remember 


76       AN  INTRODUCTION  TO   PHYSICAL   GEOGRAPHY 

is  that  such  rock  is  built  out  of  small,  separate  grains  and 
may  return  to  its  former  condition. 

65.  Shale. — There  is  a  very  fine-grained,  soft  rock, 
which  splits  easily  into  thin  leaves  along  its  planes  of 
bedding.  In  an  exposed  ledge,  thin  fragments  and  slivers 
of  such  a  rock  will  have  formed  a  slope  of  easily  sliding 
waste,  and  such  waste,  used  for  mending  roads,  may  swiftly 
turn  into  mud  as  rain  falls  on  it  and  vehicles  crush  it. 
We  call  such  rock  Shale,  and,  like  the  sandstone,  it  consists 
of  small  bits  of  mineral  bound  together.  The  differences 
are :  first,  that  the  shale  often  contains  much  of  the  fine, 
smooth  substance  (an  aluminum  silicate)  which  is  known  as 
Clay,  and,  second,  that  the  other  minerals  in  the  shale  are 
more  finely  pulverized  than  the  grains  in  a  sandstone. 

66.  Limestone. — A  soft  mineral,  known  as  calcium  car- 
bonate, makes  up  the  bulk  of  this  rock.  It  may  have  various 
colors,  due  to  impurities  which  it  contains,  hence  we  see 
blue,  gray,  yellow,  and  black  limestones.  A  very  pure  and 
light  gray  or  white  limestone,  called  Chalk,  occurs  in  parts 
of  Texas,  Kansas,  and  Iowa,  and  especially  in  England. 
It  is  soft  and  fine-grained.  Limestone  is  used  for  build- 
ing, and  is  often  "  burnt "  for  quicklime.  The  burning 
changes  the  calcium  carbonate  to  calcium  oxid  or  lime. 
A  very  compact  and  crystalline  variety  is  known  as  Marble. 
Limestone  will  dissolve  more  readily  in  water  than  most 
other  rocks  (see  Fig.  55).  It  was  originally  made  by  the 
deposit  of  the  hard  parts  of  lowly  creatures.  Such  animals 
unconsciously  gather  dissolved  calcium  carbonate  from  the 
waters  in  which  they  live,  and  build  it  into  shells.  Thus 
we  see  how  limestones  are  brought  together,  and  how  they 
may  waste  and  disappear  again. 

67.  Granite. — The  three  kinds  already  studied  are  the 
chief  rocks  that  are  made  or  accumulated  in  water.  Many 
rocks  are  the  product  of  heat,  either  deep  down  in  the 
crust  of  the  earth,  or  acting  in  the  outflow  of  lava  from 
volcanic  openings.     Basalt  belongs  to  the  latter  class.     It  is 


WEATHERING  AND  SOILS  7Y 

dark,  heavy,  and  contains  much  iron.  Granite  is  a  com- 
mon building  stone,  and  samples  may  be  seen  by  all.  It 
belongs  to  the  first-named  class  of  igneous  rocks,  those 
formed  far  below  the  surface  and  brought  to  light  by  the 
removal,  through  the  ages,  of  the  overlying  rocks. 

The  chief  minerals  in  the  common  granite  are  three. 
If  the  student  will  look  carefully  he  will  see  glassy  bits  of 
a  very  hard  mineral.  This  is  Quartz.  He  may  also  see 
a  pink,  greenish,  or  white  mineral.    This  is  Feldspar.    There 


Fig.  53.— Granite. 


are  also  scales,  often  very  small,  of  the  shiny,  thin-splitting 
mineral  known  as  Mica.  These  three  minerals  are  massed 
together  in  finer  or  coarser  fragments,  to  make  up  the  rock. 
Anything  that  will  tear  these  mineral  bits  apart  will  cause 
the  rock  to  break  down.  One  of  the  three,  the  feldspar, 
decays  slowly  under  the  weather,  and  much  of  it  becomes 
in  time  a  smooth  clay.  In  the  city  of  Washington  there 
are  places  where  the  rotted  granite  could  be  excavated  with 
a  spade. 

These  are  but  a  few  out  of  many  kinds  of  rocks,  but 
they  will  serve  as  examples  to  show  how  all  rocks  are  built 


78      AN  INTRODUCTION  TO  PnYSlCAL  GEOGUAPHY 


up  of  mineral  particles  and  may  be  broken  down  again. 
It  is  to  such  breaking  down  that  the  diversity  of  the 
earth's  surface,  the  forms  of  its  hills  and  mountains,  and 
the  existence  of  its  mantle  of  soil,  are  largely  due. 

To  a  short  study  of  these  processes  of  destruction  we 
now  turn.  Eocks  are  broken  and  worn  by  river  action, 
as  we  have  seen ;  and  other  chapters  will  show  how  they 
yield  to  the  friction  of  glaciers  and  the  pounding  of  sea- 
waves.  The  destructive  processes  referred  to  in 
^HB  this  chapter  are  less  conspicuous,  though  per- 
PPUP^  ^         haps  more  important. 

Surface  Wasting 

68.  The   atmosphere.  —  Our    at- 
mosphere contains  much  oxygen,  a 
gas  which  combines  readily  with 
most  substances.    When  it  unites 
with  iron  it  causes  rust,  and  rust- 
ing   involves    softening,    and    a 
change  to  dull  brown  or  reddish 
color,    in    place  of    the    former 
metallic  luster.     Most  rocks 
contain  iron  in  some  form, 
the  rusting  of  which  causes 
the  rocks  to  show  stain  and 
by  and  by  to  decay.     This 
is    one    important    case    of 

is  composedof  horizontal  layers:  and     ^^eathcring,    a    term    which 
is   divided  by  vertical   joints.      The     is  USCd   to   COVCr   the    SOftCU- 


Fig.  54.— Weathered  sandstom 


weathering  is  most  rapid  along  joints 
and  at  the  divisions  between  layers. 


ing  and  breaking  up  of  rocks 
which  in  a  number  of  ways 
goes  on  quietly  at  the  surface  of  the  earth.  The  surface 
of  a  stone  block  or  boulder  is  often  thus  changed,  while 
the  inner  parts,  if  opened  to  view  by  the  hammer,  show 
the  true  color  and  hardness  of  the  rock.  A  bed  of  clay 
or  sand  is  usually  weathered  to  dull  hues  above,  but  re- 


WEATHERING  AND  SOILS 


79 


mains  of  a  bluish  color  below.     This  change  is  due  to  the 
oxygen  of  the  air,  which  penetrates  all  parts  not  filled 


Fig.  55.-— Weathered  limestone.    Wasting  is  by  solution.    Water  finds  readiest  access 

along  joints. 


by  water.  Marble  tombstones  lose  their  polish  after  a 
few  years.  Eain  and  ajir,  holding  small  amounts  of 
carbon  dioxid  and  other  gases,  dissolve  a  little  of,  the 
surface  and  so  remove  the  luster.  Cleopatra's  N"eedle,  a 
granite  shaft  now  standing  in  Central  Park,  New  York, 
was  preserved  for  many  centuries  in  Egypt,  where  the  air 
is  exceedingly  dry;  but  its  surface  was  found  to  need 
some  protective  wash  when  exposed  to  the  damper  air 
of  the  Atlantic  coast,  especially  where  mingled  with  the 
7 


80      AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


gases  that  flow  from  the  chimneys  of  a  great  city  (see 
Fig.  57). 

69.  Rain  wash. — Notice  a  bank  of  earth  just  after  a 
heavy  shower.     The  soil  crumbles  and  its  grains  freely  fall 


Fig.  56.— a  pebbly  rock  carved  by  rain  ;  Russian  River,  Gal. 

apart.  There  are  small  furrows  or  channels  down  the  slope, 
and  rills  of  water,  still  running  in  the  channels,  are  dark 
with  the  grains  of  earth  they  have  been  able  to  pick  up. 
Permanent  streams  work  only  on  narrow  strips  of  land,  but 
rain  soaks  and  softens  the  rocks  and  soil  everywhere  and 


WEATHEEING  AND  SOILS  81 

gives  the  first  start  to  loosened  particles.  The  rain  rills 
begin  the  great  task  of  carrying  which  the  creeks  and 
rivers  continue. 

70.  Solution. — If  a  gallon  of  "water  from  any  stream  or 
well  were  evaporated,  a  small  amount  of  solid  matter  would 
be  found.  In  a  tea-kettle  much  water  is  evaporated,  and 
still  more  in  a  steam-boiler,  and  the  inner  surface  of  each 
receives  a  hard  coating.  This  solid  matter  has  been  dis- 
solved from  the  rocks  by  water.  Thus  whether  we  observe 
that  the  damp  air  changes  the  polished  marble  to  a  dull 
surface,  or  remark  that  some  water  is  "  hard  "  and  other  is 
"  soft,"  we  are  noting  the  effects  of  solution  upon  the  rocks 
of  the  earth's  crust. 

71.  Frost  and  changes  of  temperature. — The  wasting  of 
Cleopatra's  Needle  was  due  not  only  to  the  oxygen  and 
other  gases  of  the  air,  and  to  solution,  but  to  the  freezing 
and  thawing  of  its  moistened  surface.  Even  in  summer  the 
heating  and  swelling  under  the  hot  sun  of  noon,  and  the 
cooling  and  shrinking  of  night,  will  make  some  rocks 
crack  and  flake.  The  student  should  examine  stone  build- 
ings, and  he  will  be  sure  to  find  cracks  and  signs  of  decay 
of  which  there  was  no  indication  when  the  buildings  were 
made.  Dr.  Livingstone  records  in  his  notes  such  cracking 
of  the  rocks  of  Central  Africa,  where  the  noon  temperature 
was  137°  F.  The  upper  slopes  and  top  of  Pikes  Peak  are 
covered  with  a  mantle  of  sharp-edged  granite  boulders 
riven  from  the  bed-rock  of  the  mountain  by  changes  of 
temperature,  together  with  the  freezing  of  water  which 
soaks  into  crevices  (see  Fig.  122). 

72.  Plants. — All  trees  which  have  strong  tap-roots  stir 
the  earth  to  a  considerable  depth,  and  even  grasses  often 
send  their  slender  roots  two  feet  into  the  ground.  "When 
plants  die  their  roots  decay,  and  the  process  of  decompo- 
sition produces  new  substances,  some  of  which  are  power- 
ful to  produce  decay  in  rocks.  As  trees  and  herbs  grow 
everywhere,  thrusting  the  earth  apart  by  their  roots,  and 


Fig.  57.— Weathering  of  limestone  in  the  wall  ot  an  old  building  ;  Trinity  College, 
Oxford,  England. 


WEATHERING   AND  SOILS  83 

mixing  with  it  in  their  decay,  we  can  see  that  the  influence 
of  plants  is  almost  universal. 

A  gorge  should  be  visited  and  a  study  should  be  made 
of  the  roots  of  the  trees  on  its  steep  slopes  and  crests.  The 
roots  thrust  themselves  far  into  the  joints  and  planes  of 
bedding  and  rend  the  rocks  apart  with  great  power.  At 
the  same  time  mosses  mantle  many  rock  surfaces,  keeping 
them  moist,  and  thus  helping  water  to  do  its  work  of 
destruction. 

73.  Animals. — The  prairie-dog  is  widely  found  in  the 
western  United  States.  It  digs  deep  burrows,  and  casts 
up  at  the  mouth  of  each  one  a  mound  of  earth.  The 
"  villages "  inhabited  by  these  creatures  sometimes  cover 
many  acres.    Thus  a  large  work  is  done  by  them  in  stirring 


Fig.  58.— Ant-hill ;  Arkansas  Valley,  Colo.    Height,  about  one  foot. 

the  earth  at  its  surface  and  a  little  below.  Of  similar  effect 
is  the  work  of  woodchucks  and  the  elaborate  system  of  tun- 
nels made  by  ground-moles.  In  like  manner  crawfishes  bur- 
row deeply,  and  it  is  said  that  they  have  even  caused  breaks 
in  the  levees  of  the  Mississippi  Eiver.  Beavers  and  musk- 
rats  carry  on  their  operations  at  the  borders  of  streams,  and 
the  beavers  cut  much  small  timber,  flood  many  acres  by 
their  dams,  and  have  been  known  to  excavate  canals  for 
floating  wood  to  their  ponds  (see  Fig.  234).  The  hillocks 
built  by  ants  are  composed  of   sand-grains  brought  from 


84      AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

tunnels  underground,  and  are  in  some  places  so  numerous 
as  to  make  a  dotted  pattern  on  the  hillside. 

Near  the  close  of  his  life  Darwin  took  to  his  publisher 
a  manuscript  of  which  he  spoke  in  modest  terms.  It  was 
published,  and  has  become  famous,  because  it  shows  how 


Fig.  59.— Shale  broken  by  down-hill  creep  ;  Colnmbia,  Pa. 


large  a  work  the  common  earthworm  does  in  pulverizing 
the  soil  and  mingling  the  substances  which  compose  it. 
And  we  must  not  fail  to  see  m  man  himself  a  vigorous 
modifier  of  the   earth's   surface.     He  causes  changes  in 


WEATHERING  AND  SOILS  85 

many  ways,  but  the  most  important  is  by  clearing  the 
forests  and  turning  up  the  earth  with  the  plow.  Thus 
rains,  frosts,  winds,  and  surface  streams,  all  are  given  a 
chance  to  work,  and  the  decay  and  transfer  of  the  mate- 
rials of  the  earth's  surface  are  much  hastened. 

74.  Creep. — When  the  farmer  runs  a  side-hill  plow  along 
a  steep  slope  he  turns  the  soil  toward  the  bottom  of  the 
hill,  and  in  so  doing  he  assists  in  a  work  on  which  nature  is 
ever  engaged.  As  the  friction  between  particles  is  lessened 
by  the  entrance  of  water,  and  as  the  soil  is  slightly  moved 
by  cooling  and  warming,  freezing  and  thawing,  its  weight 
pulls  steadily  in  one  direction,  and  this  causes  a  real  but  im- 
perceptibly slow  down-hill  movement  which  we  call  Creep. 
On  steep  mountainsides  this  of  course  progresses  less  slowly 
than  on  ordinary  sloping  fields. 

75.  Rock  falls. — Where  rivers,  or  the  sea,  are  undermin- 
ing a  cliff,  or  where  a  cliff  has  in  any  way  been  formed, 
masses  of  the  upper  rocks  come  to  be  insecurely  supported. 
Frosts  and  roots  use  their  thrusting  power,  joints  are 
opened,  and  blocks  tumble  to  the  bottom.  Thus  gravita- 
tion aids  in  the  destruction  of  the  lands. 

76.  Avalanches. — Masses  of  snow  losing  their  poise  on 
high  mountain  slopes  go  down  with  fearful  speed  and  de- 
structive power.  Tbey  cut  such  lanes  through  the  forests 
as  may  be  seen  in  the  Kocky  Mountains  or  the  Alps  (Fig.  60), 
and  sweep  rocks  and  earth  in  their  course.  The  Swiss 
people  set  rows  of  strong  stakes  across  the  slopes  where 
avalanches  are  in  the  habit  of  starting,  and  thus  check  the 
snows  above  their  farm  plots  and  villages. 

77.  Thickness  of  land  waste. — When  a  surveyor  or  con- 
tractor estimates  the  cost  of  making  railway  cuttings  or 
canals,  he  takes  into  account  the  thickness  of  the  earthy 
mantle  that  covers  the  rock.  The  excavation  may  be 
partly  in  waste  and  partly  in  rock,  according  to  its  depth 
and  the  thickness  of  the  waste  cover.  The  latter  varies 
much  from  point  to  point.     In  many  valleys  the  deposits  of 


Pig.  60. — Avalantiie  tracks  ihrough  a  forest  of  fir  ;  northern  Montana.     The  moun- 
tainside was  worn  smooth  and  steep  by  a  great  glacier,  and  bears  little  soil. 
86 


WEATHERING  AND  SOILS  87 

clay,  sand,  and  gravel  are  several  hundred  feet  deep.  But 
often  on  the  uplands  and  sometimes  in  valleys  the  rock 
comes  to  the  surface.  Thus  the  earthy  cover  varies  from 
slight  to  great  depth,  but  if  we  dig  deep  enough  the  solid 
rock  will  be  found. 

78.  Local  waste. — If  a  rock  decays  in  its  original  place, 
as  through  wetting  and  drying,  freezing  and  thawing,  and 
the  agency  of  roots,  the  earth  and  soil  may  be  called  local. 
Some  of  the  materials  once  forming  the  surface  will  have 
been  dissolved  and  carried  away,  but  the  parts  not  readily 
dissolved  will  remain.  Hence  the  rock  controls  the  soil. 
Such  is  the  case  with  the  soils  of  Kentucky  and  Tennessee. 
Limestones  make  the  rich  "  Blue  Grass  region  "  of  Ken- 
tucky, and  sandstones  make  the  poorer  parts  of  the  State. 

79.  Transported  waste. — The  soils  of  the  central  valley 
of  California  have  mainly  come  down  from  the  Sierras  by 
the  wash  of  the  rivers.  The  soils  of  Louisiana  have  been 
brought  from  the  Eocky  Mountains,  from  the  Great  Plains, 
from  the  prairies,  and  from  the  plateaus  and  mountains  of 
the  Appalachian  region.  They  have  been  transferred  by 
the  Mississippi  and  its  branches.  The  earthy  mantle  of 
Connecticut  and  Rhode  Island  is  in  part  composed  of  rock 
flour  and  stones  brought  from  Massachusetts  and  the 
northern  Xew  England  States.  The  Connecticut  and  other 
rivers  have  done  some  of  this  work,  but  much  more  is  due 
to  the  great  glacier  that  moved  south  over  that  region.  In 
the  northeastern  United  States  the  waste  mantle  is  com- 
posed in  part  of  local  rocks,  and  in  part  of  rocky  matter 
moved  from  the  north  by  glacier  currents.  We  thus  speak 
of  transported  waste,  or  Drift,  a  word  especially  applied  to 
material  moved  by  glaciers. 

Lai^td  Forms  Due  to  Surface  Wastikg 

80.  Mountains.— The  Catskill  Mountains  of  ^ew  York,  or 
Greylock,  Wachusett,  and  Monadnock  in  Xew  England,  do 
not  stand  forth  as  mountains  because  they  have  been  lifted 


88      AN  INTRODUCTION   TO  PHYSICAL  GEOGRAPHY 

above  the  surrounding  country,  but  because  the  surround- 
ing lands  have  wasted  away,  and  their  materials  have  been 


Fig.  61.— Granite  crags  in  the  Black  Hills  of  South  Dakota. 


carried  to  the  sea.  In  like  manner,  the  mountain  ridges 
of  Pennsylvania  and  Virginia  are  from  one  to  four  thou- 
sand feet  higher  than  the  valleys  that  run  between  them ; 
and  this  is  not  because  of  a  difference  in  uplift,  but  is  due 
to  the  wasting  of  the  softer  rocks.  The  country  has  grown 
rough  in  time,  as  a  smoothed  surface  of  a  coarse-grained 
wood  does,  after  years  of  exposure  to  the  weather. 

It  is,  however,  true  that  many  mountain  masses  are 
higher  than  the  adjoining  lands  ever  were.  The  Kocky 
Mountains,  for  example,  have  always  been  much  higher 
than  the  Great  Plains,  though  both  have  suffered  uplift 
(see  Chapter  VIII). 


WEATHERING  AND  SOILS 


89 


81.  Rock  ledges  and  waste  slopes. — Almost  every  moun- 
tain or  steep  liill  shows  us  ledges,  or  sometimes  long  benches 
or  shelves,  of  harder  rock,  which  resists  the   destroying 


Fig.  62. 


Hog-back,"  near  Cariyon,  Colo.    A  small  mountain  ridge,  due  to  the  un- 
equal wasting  of  strong  and  weak  rocks.    See  Fig.  63. 


forces  we  have  been  studying,  while  between  the  ledges 
are  smooth  slopes  of  soil  or  coarser  rocky  waste  (see  Fig. 
64).      In  time   the    ledges   will    crumble   away  and  the 


w  s  w  s  wswsw 

Fig.  63.— Section  of  the  ridges  and  valleys  shown  in  Fig.  62.  S,  8,  S  are  strong 
rocks  ;  W,  W,  W,  weak  rocks.  The  rocks  were  once  more  extensive,  as  indi- 
cated by  the  broken  lines. 


slopes  will  take  full  possession.     These  changes  are  seen  to 
good  advantage  in  many  parts  of  the  far  West  where  the 


SV" 


Fig.  64. — Rock  ledges  Uiuiestoue  and  eandijtone)  and  wjt^U'  ^iujiLS  (concealing  shale); 
Grand  Canyon  of  the  Colorado  River,  Arizona.    See  page  89. 

90 


WEATHERING  AND  SOILS 


91 


rocks  are  horizontal,  with  harder  and  softer  layers,  and 
there  is  so  little  vegetation  that  the  forms  of  the  hillsides 


Fig.  65.— a  mesa-butte  in  Oklahoma.    At  the  left  is  the  profile  of  a  mesa  at  the  same 
level.    The  butte  was  once  part  of  the  mesa. 

are  fully  exposed  to  view.  Sometimes  the  upper  surface  of 
a  horizontal  hard  bed  is  bare  over  a  considerable  area, 
while  the  edge  is  kept  as  a  cliff  by  the  weathering  of  soft 


Fig.  66.— Bad  lands  near  the  Diablo  Mountains,  Texas. 
by  a  line  of  cliffs. 


Each  hard  stratum  is  marked 


beds  below.     Such  a  shelf  or  table  is  called  a  Mesa.     If  the 
broadening  of  valleys  divides  a  mesa  so  that  part  of  it 


Fig.  67.— Bad  lauds  of  South  Dakota. 


Fig.  68.— Hills  and  mountains  of  the  Appalachian  system,  showing  rounding  of  sum- 
mits. 
92 


WEATHERING  AND  SOILS 


93 


stands  as  a  separate  hill  (Fig.  65),  the  hill  is  called,  in 
the  same  western  region,  a  Butte,  or  Mesa-Butte. 

82.  Bad  lands. — On  slopes  where  the  soil  is  poor,  or  for 
any  other  reason  plants  do  not  grow,  decay  is  slow,  and 
wear  by  running  water  comparatively  rapid.     Kavines  ex- 


MiHHnMiiiiiii 

-Mount  Sneffels,  Colorado,  a  sharp-crested  mountain. 

tend  and  branch  until  the  whole  area  is  carved  into  narrow, 
steep-sided  ridges  and  hills.  Such  tracts  occur  most  fre- 
quently in  the  drier  parts  of  our  Western  States,  where 
they  are  called  Bad  Lands,  because  unfit  alike  for  tillage 
and  grazing  (see  Figs.  66  and  67). 


94:      AN  INTRODITCTION  TO  PHYSICAL  GEOGRAPHY 

83.  Sharp  peaks  and  rounded  summits. — Any  good  picture 
of  the  southeastern  ranges  of  the  Appalachian  system  will 
show  how  round  and  subdued  the  mountain  tops  are  (Fig.  68). 
Long  ages  of  weathering  have  caused  this.  But  the  San 
Juan  Mountains  of  Colorado,  the  Canadian  Eockies,  the  Alps, 
and  the  Pyrenees  bristle  with  sharp  ridges  and  peaks  (Figs. 
69  and  134).  These  mountains  have  existed  long  enough  to 
have  deep  narrow  valleys  and  steep  slopes  made  by  weather- 
ing, streams,  and  glaciers,  but  not  long  enough  to  have  their 
sharp  crests  subdued.  These  are  samples  of  the  ways  in 
which  wasting  controls  the  shapes  of  the  earth's  surface. 

Soils 

84.  What  soil  is. — The  student  should  observe  any  exca- 
vation that  penetrates  a  few  feet  below  the  surface.  For  a 
few  inches,  or  one  or  two  feet,  the  material  will  be  dark  in 
color  and  mixed  with  living  roots  and  decayed  vegetable 
matter.  The  latter  may  be  present  in  small  measure,  or  it 
may  abound,  even  making  the  surface  matter  almost  black. 
This  superficial  layer  is  called  the  Soil.  It  is  the  support 
not  only  of  the  natural  growth  of  land  plants,  but  of  all 
cultivated  plants.  Its  origin  is  therefore  interesting,  and 
no  other  material  consideration  is  so  important  to  our  race 
as  its  preservation. 

85.  Origin  of  soil.— It  will  be  observed  that  we  have 
carefully  avoided  using  the  word  soil  in  writing  of  the 
general  waste  mantle,  although  it  is  often  loosely  so  used. 
The  student  should  distinguish  clearly  and  use  it  only  of 
that  outer  layer  of  earth  which  is  specially  fitted  to  support 
life.  Like  the  waste  that  lies  below  it,  the  soil  is  derived 
from  the  solid  rocks,  but  it  alone  is  enriched  by  the  addi- 
tion of  vegetable  matter.  The  chief  foods  of  growing  plants 
are  water  and  certain  substances  contained  in  air,  but  they 
need  also  something  contained  in  rock  waste,  and  the  de- 
caying vegetable  matter  in  the  soil  helps  to  prepare  the 
waste  for  their  use. 


WEATHERING  AND  SOILS  96 

86.  Kinds  of  soil. — All  farmers  roughly  classify  their 
soils.  A  clayey  soil  they  call  heavy,  and  are  careful  not  to 
work  it  when  it  is  too  wet.  Otherwise  it  bakes  and  is  un- 
productive. A  sandy  soil  they  call  light.  It  requires  abun- 
dant moisture,  else  the  water  leaches  off  and  the  roots 
can  not  nourish  the  plant.  The  best  soils  are  mixtures  of 
clayey  and  sandy  waste,  and  are  called  loams,  which  also 
are  said  to  be  light  or  heavy  according  to  their  character. 
As  soils  are  of  many  kinds,  it  is  fortunate  that  the  needs  of 
plants  are  also  varied,  so  that  some  can  thrive  where  others 
would  perish.  Swamp  soils  are  often  made  available  by 
drainage,  and  are  of  great  value,  especially  for  truck  farm- 
ing. Lime,  potash,  and  phosphates  are  among  the  soil 
elements  that  plants  use  most,  although  they  make  but  a 
small  portion  of  the  entire  soil.  Hence  they  may  become 
exhausted,  and  the  prudent  farmer  "  rotates  "  his  crops  and 
adds  fertilizers,  to  keep  up  a  due  supply  of  these  materials. 

87.  The  use  of  soil  depends  on  climate. — Wheat  thrives  in 
Manitoba,  corn  in  Illinois,  and  cotton  in  Mississippi.  The 
soils  are  not  indeed  the  same,  but  the  principal  difference 
is  in  the  climate,  which  makes  soils  useful  for  certain 
crops.  In  the  western  part  of  the  Great  Plains,  and  in  the 
valleys  farther  west,  there  is  so  little  rain  that  our  food 
plants  do  not  thrive,  but  wherever  the  needed  water  can 
be  supplied  by  irrigation  good  crops  can  be  raised.  There 
is  no  reason  to  doubt  that  the  soils  of  northern  Siberia  are 
as  rich  as  those  of  southern  Europe,  but  the  temperature  is 
hostile  to  agriculture. 

88.  Soils  of  the  United  States. — These  depend  on  the 
forces  which  have  made  them.  As  we  have  seen,  those  of 
New  England  are  largely  transported  soils.  On  Cape  Cod 
and  Marthas  Vineyard  they  are  sandy.  On  the  uplands  of 
Massachusetts  they  are  clayey,  depending  thus  on  the  action 
of  the  glacier  in  its  moving  and  melting.  This  will  be  bet- 
ter understood  after  the  study  of  glaciers.  Then,  too,  the 
student  will  learn  what  parts  of  our  country  were  affected 

8 


96       AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

by  the  ice  invasion.  South  of  the  ice  limit,  as  in  Virginia, 
Kentucky,  and  other  States,  the  soil  is  made  of  the  local 
rocks,  and  is  clayey,  sandy,  and  rich  or  poor  in  lime  and 
other  elements,  according  to  the  nature  of  the  bed-rocks 
and  the  character  of  weathering.  Much  of  the  soil  of  the 
Gulf  region  is  of  alluvial  or  river-borne  material.  Around 
the  borders  of  our  Great  Lakes  are  tracts  of  level  land 
mantled  over  with  lake  muds  deposited  when  the  waters 
stood  at  a  higher  level.  Thus  every  soil  has  a  history,  and 
its  origin  is  in  some  way  related  to  the  changes  by  which 
the  lands  have  come  to  their  present  condition.  It  is  of 
interest  to  add  that  the  Department  of  Agriculture  has 
organized  a  division  for  the  study  and  mapping  of  the 
soils  of  the  United  States. 

Undergbound  Changes  in  the  Earth's  Crust 

89.  Water  in  the  rocks. — If  a  piece  of  common  clay  or  a 
handful  of  soil  be  dried  in  an  oven  it  will  lose  considerable 
weight,  thus  showing  that  a  large  amount  of  water  was 
held  among  the  mineral  fragments.  Samples  of  dry  sand  in 
Colorado  have  been  found  to  absorb  water  to  the  extent  of 
29  per  cent  of  their  volume.  If  a  boring  be  made,  water 
will  generally  be  found  before  great  depths  are  reached. 
There  is  often  an  abundant  supply  within  a  few  feet  of  the 
surface.  Quicksand  is  only  a  fine  sand  so  filled  with  water 
that  its  grains  move  with  little  friction,  and  it  readily  en- 
gulfs man  or  beast  that  seeks  to  traverse  it.  All  the  deeper 
and  solid  rocks  also  contain  water.  Xo  granite  is  so  hard 
and  compact  that  it  does  not  hold  among  its  mineral  par- 
ticles a  small  percentage  of  water. 

This  water  is  nearly  stationary  in  hard  rocks  which 
are  not  crossed  by  cracks.  But  where  there  are  fissures 
it  circulates  with  more  or  less  freedom.  Through  beds 
of  sand,  and  particularly  in  layers  of  gravel,  water  will 
flow  readily,  though  much  more  slowly  than  in  a  surface 
stream.      The  fact  that  water  is  present  and   moves  in 


WEATHERING  AND  SOILS 


97 


rocks,  leads  to  important   changes,  several  of  which  we 
shall  now  study. 

90.  Hardening  of  rocks. — Ground-water,  coming  in  con- 
tact with  the  minerals  that  make  up  the  rocks,  is  able  to 
take  more  or  less  of  the  substances  into  solution.  Thus  it 
may  take  up  calcium  carbonate,  iron,  and  many  other  min- 
erals ;  continuing  its  course  through  the  rocks,  it  may  after- 
ward deposit  part  of  this  dissolved  matter  among  the  parti- 
cles and  bind  them  more  firmly  together,  as  by  a  cement.  In 
a  large  gravel-pit  one  can  usually  see  projecting  layers  of 
gravel,  whose  pebbles  and  sand-grains  have  been  thus  bound 
together  by  an  underground  deposit  of  calcium  carbonate. 

91.  Mineral  veins. — Water  laden  with  dissolved  minerals 
often  flows  through  a  fissure,  and  deposits  part  of  its  burden 
on  the  walls,  until  the 
fissure  is  filled  with 
mineral  substances 
different  from  the  ad- 
joining rocks.  On 
breaking  the  rock, 
this  Vein,  as  it  is 
called,  appears  like  a 
narrow  or  wide  rib- 
bon, whose  color  de- 
pends on  the  mineral 
deposited.  Many  veins 
are  of  white  quartz, 
and  sometimes  the 
quartz  contains  gold, 
in  particles  often  too  small  to  be  seen  by  the  unaided  eye. 
Much  of  the  gold  of  California  and  Colorado  occurs  in  veins 
of  quartz  or  some  other  mineral,  and,  indeed,  veins  contain 
the  most  important  deposits  of  the  precious  metals.  The 
metals  have  been  dissolved  from  the  rocks  in  which  their 
particles  were  scattered,  and  brought  together  by  under- 
ground waters. 


Fig.  70. 


-A  vein  of  gold-bearing  quartz 
City,  Cal. 


Nevada 


98       AN   INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

92.  Destruction  of  rocks  by  underground  waters. — We 

must  now  look  at  another  side.  As  already  mentioned,  the 
mineral  matter  contained  in  underground  waters  has  been 
obtained  by  solution  from  rocks.  What  the  water  has 
gained  the  rocks  have  lost,  and  the  effect  on  the  rocks  has 
often  been  to  break  them  up  into  grains.  In  Cornwall, 
England,  the  granites  are  sometimes  completely  decayed  to 
a  depth  of  several  hundred  feet.  Sandstone  boulders  and 
beds  of  sandstone  become  heaps  and  beds  of  sand  in  this 
manner.  In  other  cases  the  whole  substance  of  a  rock  is 
removed,  and  this  brings  us  to  the  formation  of — 

93.  Caverns. — The  Mammoth  Cave  in  Kentucky  consists 
of  a  complicated  network  of  passages,  having  a  total  length 


Fig.  71.— Sink  hole  and  lake,  Kansas.    In  this  case  the  rock  dissolved  beneath  was 

probably  salt. 


of  two  hundred  miles  or  more.  It  has  been  thoroughly 
explored  and  mapped.  It  is  entirely  dug  out  of  limestones. 
Water,  which  dissolves  limestone  more  readily  than  most 


WEATHERING  AND  SOILS 


99 


other   rocks,  filters    along   the    joints    and   crevices,  and 

gnaws  incessantly  until  great  openings  result.    The  calcium 

carbonate  is  carried  off   by 

underground     drainage    to 

some  point  where  the  water 

joins  a  surface  stream,  and 

thence  it  goes  out  into  the 

sea.      Beds  of  gypsum  and 

rock  salt  are  dissolved  even 

more  rapidly.    Fig.  55  shows 

the  mouth  of  a  small  cavern 

made  by  the  enlargement  of 

a  joint  in  limestone. 

When  a  considerable 
area  has  been  thus  under- 
mined, the  upper  rocks  may 
cave  in,  thus  letting  down 
the  surface  of  the  land 
above.  Many  small  lakes 
in  Kentucky  occupy  such 
Sink  Holes.  A  stream  may 
flow  for  a  considerable  dis- 
tance in  a  tunnel  thus  made. 
As  the  tunnel  grows  broader, 
its  roof  at  length  falls  in, 
making  an  open  ravine.  If 
a  small  section  of  the  roof 
remains  in  place,  we  have  a 
bridge.  Such  is  the  origin 
of  the  Natural  Bridge  of  Virginia,  over  which  a  public 
highway  passes.  Another  such  bridge  in  the  same  State 
is  a  half  mile  in  extent,  and  a  railway  which  follows  the 
stream  beneath  it  thus  threads  a  natural  tunnel. 

94.  Stalactites  and  stalagmites. — The  water  dripping  from 
the  roof  of  a  cavern  has  soaked  through  the  limestones 
above  and  brought  out  its  load  of  calcium  carbonate.    Some 


Fig.  72.— Stalactites,  Lnray  Cavern,  Vir- 
ginia. Photograph  by  C.  H.  James  ; 
copyrighted. 


100    AN  INTRODUCTION   TO   PHYSICAL  GEOGRAPHY 

of  this  is  deposited  at  the  point  where  the  water  comes  out, 
and  a  mass  like  an  icicle  grows  downward.  Where  the 
drip  is  along  a  cr^ck,  the  mass  will  be  blade-shaped  instead 
of  needle-shaped.  As  it  grows  downward  it  also  increases 
in  diameter  by  the  addition  of  outer  layers,  like  the  rings 
of  a  tree.  Such  a  formation  is  a  Stalactite.  Luray,  the 
most  famous  and  beautiful  of  the  caverns  of  Virginia,  is 
noted  for  its  stalactites,  many  of  which  are  large  and  finely 
colored  by  various  minerals,  mixed  in  small  quantities 
with  the  calcium  carbonate. 

The  dripping  water  strikes  the  floor  of  the  cavern  and 
there  deposits  more  of  its  mineral  burden,  which  thus 
builds  a  small  mound  called  Stalagmite.  Sometimes  the 
stalagmite  forms  a  pavement  over  a  considerable  surface. 

95.  Caverns  and  living  creatures. — Blind  fishes  and  other 
curiously  modified  animals  are  found  in  caverns.  Such 
changes  have  come  about  by  successive  generations  of  these 
creatures  living  in  the  cavern,  where  the  eye,  for  example, 
from  lack  of  light,  has  grown  useless,  or  has  disappeared. 
Many  caverns  in  Europe  were  the  refuge  of  prehistoric 
men  and  animals,  whose  bones  are  now  found  there,  and 
the  remains  of  ancient  animals  have  been  found  in  Ameri- 
can caverns  also. 

96.  Springs. — When  water  has  soaked  into  the  earthy 
mantle  or  the  under  rocks,  and  issues  at  the  surface  at  a 
lower  level,  we  call  the  outflow  a  Spring.  Coming  out  from 
a  depth  to  which  the  warmth  of  summer  does  not  penetrate, 
spring  water  is  usually  cool,  and  its  temperature  does  not 
change  from  season  to  season.  The  size  of  a  spring,  like 
the  size  of  a  river,  is  related  to  the  area  from  which  the 
water  is  gathered.  An  underground  river  coming  to  the 
surface  makes  a  spring  of  great  volume.  At  Belief onte, 
Pa.,  at  several  points  in  Florida,  and  at  the  source  of  the 
River  Jordan,  are  such  springs. 

97.  Mineral  springs. — When  the  waters,  on  their  way 
through  the  rocks,  have  taken   a  large  amount  of  min- 


WEATHERING  AND  SOILS  101 

eral  in  solution,  this  name  is  given  to  them,  particularly 
if  the  waters  have  medicinal  value,  as  by  the  presence  of 
iron,  lithium,  sulfur,  or  other  substances.  Carlsbad  and 
Vichy  are  well-known  springs  in  Europe,  and  Saratoga  is 
the  most  famous  of  the  thousands  of  mineral  spring  locali- 
ties of  the  United  States. 


Fig.  73  —Cleopatra  Spring  and  terrace  ;  Yellowstone  National  Park,  Wyoming. 

98.  Hot  springs. — Those  of  Arkansas  will  at  once  occur 
to  the  student.  Others  are  found  at  Glenwood,  Colo.,  and 
in  the  Yellowstone  National  Park.  In  such  cases  the 
waters  have  come  up  through  heated  rocks,  and  owe  their 
temperature,  either  directly  or  indirectly,  to  the  heat  of  the 
earth's  interior.     Such  springs  are  apt  to  be  charged  with 


Fig.  74.-01(3  Faithful  Geyser,  Yellowstone  National  Park,  Wyominff 
103  ^' 


WEATHERING  AND  SOILS  103 

minerals,  because  hot  water  dissolves  the  rocks  more  readily 
than  cold  water.  Hence  also  the  waters,  losing  their  heat 
as  they  come  forth,  deposit  minerals  about  the  springs. 
Such  abundant  deposits  form  the  well-known  terraces  about 
some  of  the  springs  of  the  Yellowstone  region  (Fig.  73). 

99.  Geysers. — These  are  periodically  eruptive  springs 
found  in  the  Yellowstone  Park,  in  Iceland,  and  in  New 
Zealand.  At  intervals  of  a  few  minutes,  or  a  few  hours, 
they  spout  a  jet  of  water  into  the  air,  which  plays  like 
a  fountain  for  a  few  moments  and  subsides.  The  water 
is  boiling  hot,  and  is  mingled  with  steam.  The  explana- 
tion is  found  in  the  fact  that  the  boiling  of  water  may  be 
restrained  by  pressure.  Deep  in  the  geyser  throat  the 
water  grows  gradually  hotter,  but  for  a  time  does  not 
change  to  steam,  on  account  of  the  pressure  on  it  of  the 
water  above.  At  last  the  heat  so  increases  as  to  overcome 
the  pressure,  a  great  volume  of  steam  is  suddenly  formed, 
and  its  expansion  drives  a  quantity  of  water  into  the  air 
(see  Fig.  74). 

100.  Wells. — The  mantle  of  waste  is  usually  filled  with 
water  except  the  uppermost  part.  This  "  ground-water," 
as  it  is  called,  supplies  ordinary  springs,  and  is  itself  re- 
plenished by  the  part  of  rain  which  soaks  in.  When  a 
boring  or  digging  reaches  below  the  level  of  permanent 
ground- water  we  call  the  opening  a  well.  Water  stands  in 
it  up  to  the  ground-water  level,  and  as  this  is  pumped  or 
drawn  out  the  quantity  is  restored  by  oozing  from  the 
sides. 

101.  Artesian  wells.— These  are  so  named  from  the 
province  of  Artois  in  France.  The  principle  of  these  wells 
is  best  shown  in  Fig.  75.  The  water  soaks  into  a  porous 
bed  of  rock  such  as  a  sandstone.  It  is  kept  in  this  layer 
by  fine-grained  beds  above  and  below,  through  which 
water  does  not  readily  pass.  If  now  the  beds  all  incline  a 
little  in  one  direction  there  is  a  constant  pressure  on  the 
lower  waters  of  the  porous  bed.     If  a  boring  pierce  the 


104    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

cover  rocks,  the  waters  will  flow  out,  and  sometimes  spout 
to   a   considerable  height.      It  is  the   same  principle  of 


Fig.  75.— Ideal  section  of  a  valley,  showing  the  principle  of  artesian  wells.  A,  a 
porous  rock  ;  B,  C,  impervious  rocks  ;  F,  height  of  the  water-level  in  A;  B,  E, 
artesian  wells,  made  where  the  ground  is  lower  than  F. 

hydraulic   pressure  that  is  used   in   making  a  fountain. 

This  general  arrangement  of  porous  and  compact  beds  is 

fortunately  found  in  many 
regions.  Hence  along  the 
Atlantic  coast,  as  in  south- 
ern New  Jersey,  such 
wells  are  common,  also 
in  northern  Illinois  about 
Chicago,  and  in  many 
parts  of  the  Great  Plains 
from  the  Dakotas  to 
Texas. 

102.  Water  supply. — 
Here  we  count  springs, 
wells  of  all  kinds,  rivers, 
and  lakes,  large  and  small. 
Large  cities  obtain  their 
supplies  from  rivers  and 
lakes,  scattered  houses 
from  springs  and  wells. 
Unfortunately,  not  all 
water  is  wholesome,  and 
much  that  is  used  is  dan- 
gerous to  health  and  life. 
As  the  rain  soaks  down  to 
join  the  ground-water  it 

may  carry  with  it  any  filth  that  lies  on  or  near  the  surface, 

and  thus  make   springs  and  wells  unfit  to  use.     This  is 


Fig.  76.— Artesian  well  at  Woonsocket, 
S.  Dak.  When  photographed  the 
jet  was  97  feet  high. 


WEATHERING  AND  SOILS  105 

especially  true  in  a  village  or  thickly  settled  neighborhood, 
but  even  the  sewage  of  a  single  house  may  reach  a  well 
sunk  in  the  yard.  Every  one  should  learn  enough  about 
the  movements  of  ground-water  to  arouse  caution  in  the 
use  of  wells,  and  every  one  should  understand  that  water 
which  is  perfectly  transparent  and  pleasant  to  the  taste 
may  at  the  same  time  be  filled  with  the  germs  of  typhoid 
fever  and  other  diseases.  Eiver  supply  is  dangerous  if  the 
up-stream  region  is  thickly  settled.  Lake  supplies  are  safe 
if  due  care  be  taken  of  the  inflowing  streams.  Deep  wells, 
such  as  the  artesian,  are  likely  to  be  safe.  Increasing  atten- 
tion is  given,  as  it  should  be,  to  this  important  subject,  by 
cities  and  towns  and  by  the  State  and  National  Govern- 
ments. 

Landslides 

103.  Slides  in  railway  cuts. — In  the  spring  one  may  often 
see  reports  of  blockades  on  railway  lines  because  masses  of 
earth  have  slid  upon  the  track.  The  underground  waters 
have  lessened  the  coherence  of  the  earth,  and  the  steep 
slopes  can  no  longer  be  maintained.  Loose  waste,  as  seen 
in  talus  slopes  or  heaps  of  sand,  will  rarely  have  a  surface 
inclination  of  so  much  as  35°  with  a  level  plain.  If  this  is 
exceeded  in  artificial  slopes  of  earth,  slips  are  sure  to  take 
place. 

104.  Hillside  slips. — Small  slips  may  often  be  found  by 
the  observant  eye  on  the  slopes  of  steep  hills.  Freezing 
and  heaving  of  the  material,  followed  by  thorough  soaking, 
cause  it  to  fall  away.  On  a  larger  scale  slips  take  place 
where  rivers  undercut  the  valley  sides,  making  an  oversteep 
slope.  In  the  early  days  such  a  slide  on  the  borders  of  the 
Genesee  valley  in  western  New  York  carried  down  17  acres 
of  land,  and  the  hummocky  surface  caused  by  the  lodging 
of  the  material  is  still  to  be  seen  along  the  valley  bottom. 

105.  Seashore  slips. — In  a  similar  way  the  waves  of  the 
sea  undercut  the  shore  lands,  forming  cliffs.     A  great  slide 


I  a 


WEATHERING  AND  SOILS 


107 


of  12  acres  in  extent  once  occurred  in  this  manner  on  the 
south  shore  of  England. 

106.  Landslides  in  mountain  regions. — Here  the  valleys 
are  deep,  the  slopes  are  steep,  the  destructive  forces  are 
active,  and  everything  favors  the  sliding  of  vast  masses  of 
earth  and  rock.  In  1806  the  upper  rocks  over  a  large  area 
of  the  south  slope  of  the  Eossberg  in  Switzerland  slid  sud- 


FiG.  78.— Landslide  scenery  in  southern  Colorado.    The  monndp  in  the  valley  and  on 
the  slopes  are  masses  of  earth  and  rock  which  have  slid  from  above. 


denly  into  the  valley,  overwhelming  the  village  of  Goldau 
and  causing  the  death  of  several  hundred  of  the  inhabit- 
ants. The  earth  and  rocks,  including  masses  as  large  as 
houses,  still  strew  the  valley  for  a  distance  of  two  or  three 
miles.  The  present  village  is  built  upon  the  slide,  and  a 
railway  cut  has  been  made  through  it. 


108    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

A  still  larger  mass  broke  from  the  Cascade  Mountains  a 
few  centuries  ago  and  slid  about  two  miles  to  the  Columbia 
River,  making  a  dam  and   causing  the   "  Cascades."    A 


Fig.  79.— The  Cascades  of  the  Columbia  River.  The  central  hill  is  a  huge  boulder. 
All  the  boulders  of  the  view,  together  with  the  wooded  hill  at  the  left,  are  parts 
of  landslides. 

short  canal  has  been  made,  with  locks,  that  steamers  may 
pass,  but  above  the  dam  they  find  deep,  quiet  water  for 
thirty  miles.  In  this  deep  water  stand  stumps  of  trees 
which  grew  before  the  slide  and  were  killed  by  the  flooding. 


CHAPTEE  V 

WIND    WORK 

107.  Importance  of  winds.— We  are  studying  the  forces 
which  modify  the  crust  of  the  earth  and  change  the  forms 
of  the  land ;  hence  the  physiographic  effects  of  winds  are 
those  which  now  claim  our  attention.  In  the  chapters  on 
the  atmosphere  we  shall  consider  the  origin  and  kinds  of 
winds,  and  their  effects  on  climate  as  carriers  of  heat  and 
moisture.  The  work  of  the  ocean  depends  largely  on  the 
winds  as  wave-makers.  The  chapter  on  animals  and  plants 
will  show  how  winds  affect  the  grouping  of  many  living 
things. 

108.  Common  examples  of  wind  work. — Dust  rises  in 
clouds  from  traveled  roads,  to  settle  upon  trees,  lawns,  and 
fields.  It  gathers  in  the  gutters  of  house-roofs  and  on 
roofs  of  towers  which  are  surrounded  with  battlements. 
Seeds  brought  by  winds  or  birds  are  lodged  with  the  dust, 
and  thus  grasses,  shrubs,  and  even  small  trees  flourish  in 
such  high  places. 

109.  How  dust  is  carried. — When  very  minute  particles 
of  earth  are  mingled  with  water  we  call  them  mud ;  when 
they  are  dry  and  powdery,  dust.  The  wind,  which  is  only 
air  in  motion,  picks  them  up  just  as  moving  water  does, 
and  carries  them  till  the  motion  stops ;  then  they  settle 
slowly  down.  The  wind  does  not  blow  hard  in  the  woods, 
nor  under  thick  bushes,  nor  even  inside  the  leafy  mesh  of 
a  meadow.  It  can  pick  up  dust  only  from  bare  places, 
such  as  roads,  freshly  plowed  fields,  and  barren  deserts. 
And  when  dust  settles  from  the  air,  part  of  it  gathers 

109 


110    AN  INTRODUCTIOK  TO  PHYSICAL  GEOGRAPHY 


Fig.  80.— Profile  of  a  dune,  from  back  to  front, 
showing  its  relation  to  the  wind.  The  flow- 
lines  of  the  air  are  drawn  above,  with  the 
eddy  in  front  of  the  dune. 


among  trees  and  other  plants  where  it  is  safe  from  the 
wind.  So  the  air  is  a  carrier  of  dust,  just  as  water  is  a  car- 
rier of  mud.  It  takes  something  from  the  ground  where 
the  ground  is  bare,  and 

gives    something   to   it     

where  it  is  clothed  with 
vegetation. 

110.  How  sand  is  car- 
ried.— Sand  grains  are 
so  much  heavier  than 
particles  of  dust  that 
they  can  not  float  in  the 

air.  When  a  strong  wind  drives  them  they  go  rolling  and 
bounding  along,  and  are  rarely  raised  more  than  a  few  feet. 
Drifting  sand  often  gathers  in  wave-like  heaps  or  hills  called 
Dunes,  and  these  hills  are  not  stationary  but  travel  in  a 
curious  way.  As  the  wind  blows  across  one  of  them  its 
current  is  turned  upward  so  as  to  shoot  over  the  crest,  leav- 
ing a  quiet  spot,  or  eddy,  beyond  (Fig.  80).    While  it  is 

rising,  sand  grains  are 
dragged  along  with  it, 
but  a  little  beyond  the 
crest  they  fall  into  the 
eddy  and  come  to  rest 
on  the  lee  slope.  Thus 
the  wind  always  robs 
one  side  of  the  dune 
and  gives  to  the  other, 
and  the  position  of  the  dune  is  changed  (Fig.  81).  As 
the  dune  progresses,  a  tree  or  even  a  house  may  be  gradu- 
ally buried,  and  afterward  reappear  on  the  opposite  side. 

111.  Places  where  sand  drifts.— Forests,  thickets,  and 
meadows  protect  sand  as  well  as  dust.  So  dunes  flourish 
only  on  barren  lands.  Deserts  are  their  chief  haunts,  but 
they  find  starting-points  along  coasts,  where  waves  have 
washed  up  beach  sands ;  along  rivers,  where  sandy  bars  are 


Fig.  81.— Diagram  of  the  pi^gress  of  a  dune,  from 
a  to  h.  The  arrow  flies  with  the  wind.  A 
live  tree  standing  before  the  dune  when  it  is 
at  a  will  be  buried  by  the  advance  to  h.  An- 
other tree,  previously  killed  and  still  covered 
by  the  dune,  will  be  brought  to  light  when  it 
has  reached  h. 


WIND  WORK  111 

dried  in  summer  ;  and  in  a  few  places  where  the  mantle  of 
waste  is  so  pure  a  sand  that  plants  get  but  feeble  hold  on 
the  land. 

Flyikg  Dust  akd  Drifting  Sands  ik  Dry  Eegions 

112.  The  western  United  States. — The  plateau  regions 
west  of  Missouri  and  Iowa  are  nearly  everywhere  subject  to 
great  dust   storms.     The  climate  is  dry,  the  covering  of 


Fig.  82. — A  patch  of  grass  on  a  field  of  loose  sand.    Drifting  sand-grains  lodge  among 
the  grass,  and  a  hillock  is  built. 

vegetation  scanty,  and  winds  sweep  freely  for  hundreds  of 
miles.  The  surface  earth  is  picked  up  and  carried  in  blind- 
ing storms.  Thirty-eight  such  storms  were  reported  during 
the  years  1894  and  1895,  and  these  take  no  account  of  the 
drifting  by  every  considerable  breeze.  Great  storms  are  apt 
to  occur  on  the  plains  two  or  three  times  a  year,  and  in 
parts  of  California  they  are  more  frequent  than  this.  They 
last  from  an  hour  to  several  days,  and  hundreds  of  tons  of 
dust  are  often  borne  in  a  single  cubic  mile  of  air.  The  sun 
is  obscured  in  some  severe  storms,  and  the  sand  penetrates 
houses  and  covers  carpets  and  floors. 

Traveling  dunes  are  common  in  all  the  western  part  of 


112    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

the  Great  Plains,  in  the  region  of  the  Great  Basin,  and  in 
'New  Mexico,  Arizona,  and  southern  California. 

113.  Northern  Africa. — The  Sahara  is  not  so  completely 
a  sandy  desert  as  is  often  supposed.  Less  than  one-third 
of  the  Algerian  Sahara  is  said  to  be  covered  with  drifting 
sand.  Eocky  areas  are  not  uncommon,  and  salt  marshes, 
with  numerous  fertile  oases.  But,  as  a  whole,  the  climate 
is  dry,  and  the  winds  sweep  the  sand  over  wide  areas.  On 
the  east  the  ^Nile  Valley  receives  its  contribution  by  the 
winds,  so  that  the  sands  of  the  desert  mingle  with  the  sedi- 
ment of  the  Nile  floods. 


Fig.  83.— Dunes  in  the  canyon  of  Columbia  River.    The  wind  blows,  and  the  dunes 
migrate,  from  left  to  right. 


114.  Asia. — With  little  interruption  the  sandy  and  half- 
desert  tract  extends  from  northern  Africa  far  across  Asia. 
Oriental  explorers  and  travelers  offer  many  vivid  accounts 
of  the  desert  storms.  One  of  these,  lasting  a  whole  day, 
was  encountered  by  Dean  Stanley  on  the  borders  of  the 
Bed  Sea.  "  Imagine  all  distant  objects  entirely  lost  to  view 
— the  sheets  of  sand  fleeting  along  the  surface  of  the  desert 
like  streams  of  water ;  the  whole  air  filled,  though  invisibly, 
with  a  tempest  of  sand  driving  in  your  face  like  sleet." 


WIND  WORK 


113 


Then  follows  an  account  of  the  difficulties  of  the  caravan, 
the  Bedouins  covering  their  heads  with  their  shawls,  and 
the  camels  patiently  facing  the  blast. 


Fig.  84.— The  last  house  in  Biggs,  Ore.,  a  village  overwhelmed  by  dunes, 
to  hold  the  sand  back  by  fences  were  unsuccessful. 


Attempts 


Tn  central  China  vast  areas  are  covered,  sometimes  to 
depths  of  hundreds,  or  even  thousands  of  feet,  by  a  yellow- 
ish earth  which  is  believed  to  have  been  swept  to  its  place 
mainly  by  winds.  It  is  called  Loess,  and  is  remarkably  fine 
and  uniform  in  character.  Streams  and  even  vehicles  cut 
deep  gorges  into  it,  and  it  is  so  dry  that  in  the  bluffs 
houses  or  dugouts  are  excavated  in  which  many  Chinese 
farmers  live. 

Deiftin^g  Sai^ds  01^  THE  Shokes  of  Lakes  and  the  Sea 

115.  The  Great  Lakes.— From  the  car  window  at  Michi- 
gan City  one  may  look  upon  the  inner  slope  of  a  great,  bare 
dune,  built  by  the  winds  out  of  the  sand  on  the  shore 
of  Lake  Michigan.  Approaching  Chicago  by  one  of  the 
railways  from  the  east  one  continues  to  see  the  sands  in  a 
belt  of  hills  scantily  clad  with  trees.  Along  the  eastern 
shore  of  the  lake  are  many  dunes,  some  having  a  height  of 


114    AN   INTRODUCTION   TO   PHYSICAL  GEOGRAPHY 

200  feet ;  and  belts  of  great  dunes  are  found  on  the  bor- 
ders of  Lake  Superior. 

116.  Dunes  of  the  Atlantic  coast. — Let  us  take  Cape  Cod 
as  a  striking  example.  Thoreau,  the  naturalist,  who  many- 
years  ago  traversed  the  length  of  the  cape  on  foot,  has 
published  a  diary  giving  interesting  references  to  the  mov- 


FiG.  85.— Landward  side  of  a  dune  on  the  coast  of  North  Carolina.    Tiie  dune  is  trav- 
eling from  right  to  left,  and  has  killed  a  tree  by  burying  its  lower  part. 

ing  sands.  The  surface  earth  of  the  cape  is  a  loose  glacial 
formation,  with  much  sand  and  gravel.  For  long  ages  the 
sea  has  been  cutting  into  these  deposits  on  the  east,  and 
sorting  out  the  sand  to  make  beaches.  The  winds  blow 
freely  over  the  sea  and  play  with  the  sands  at  their  will. 
The  materials  and  the  worker  are  thus  always  at  hand,  and 
the  result  is  a  long  succession  of  shifting  sand-hills. 

We  may  now  associate  with  Cape  Cod  other  parts  of 


WIND  WORK 


115 


our  Atlantic  coast,  as  the  south  shores  of  Nantucket,  Mar- 
thas Vineyard  and  Long  Island,  and  the  Massachusetts 
coast  north  of  Cape  Ann.  Along  the  south  Atlantic  coast 
the  beds  attacked  by  wave  and  wind  and  forming  shore  dunes 
are  not  glacial,  like  many  in  New  England,  but  they  are  un- 
hardened  rocks  whose  materials  are  readily  broken  up  and 
moved  from  their  place. 

117.  Western  Europe. — On  the  coast  of  Gascony  the  belt 
of  sand-hills  is  so  continuous  that  at  only  two  points  in  a 
distance  of  a  hundred  miles  can  the  streams  find  their  way 
out  into  the  sea.  The  dunes  on  the  coast  of  Holland  cover 
a  belt  of  land  some- 
times five  miles 
wide.  The  hills  are 
usually  50  to  60  feet 
high,  but  sometimes 
rise  to  more  than 
200  feet.  Dunes 
have  been  formed 
on  the  shores  of 
Norfolk  and  Corn- 
wall, England,  and 
on  some  shores  of 
Scotland  and  Ire- 
land. 

118.  Dunes  of 
the  Mediterranean. 
—  Many  travelers 
have  described  the 
belt  of  sand-hills 
along  the  borders 
of  the  ancient  Phi- 
listia.  Ancient  cit- 
ies have  been  cov- 
ered, and  fields  and  orchards  are  often  invaded  at  the 
present  time.     The  strip  of  coastal  land  affected  is  from 


Fig.  86. 


-Planting  grass  to  stop  the  drifting  of  sand, 
near  Provincetown,  Cape  Cod,  Mass. 


116    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


one  to  four  miles  wide.  "  It  is  a  pitiful  sight,"  says  Geikie, 
"to  notice  olive  and  fig  trees  half-buried,  their  owners 
striving  hard,  season  after  season,  to  shovel  away  the  sand 
from  their  trunks,  till  they  stand,  in  some  cases,  almost  in 
pits,  which  would  close  over  them  if  the  efforts  to  save 
them  were  intermitted  even  for  a  short  time." 

119.  How  encroaching  sands  are  held  in  check. — Various 
methods  are  used.  The  French  bring  about  the  formation 
of  a  shore  ridge  of  sand  to  a  height  over  which  the  sands 
will  not  blow.  This  is  accomplished  by  artificial  barricades, 
rising  in  height  from  time  to  time,  for  a  period  of  years. 
The  principle  is  similar  to  that  used  in  making  fences  to 
stop  the  drifting  snows  at  a  certain  line.  Another  meth- 
od is  to  plant  grass  or  trees  on  the  dunes.  Common  olean- 
ders are  used  for  this 
purpose  in  Bermuda. 
The  Department  of 
Agriculture  gives  at- 
tention to  this  prob- 
lem; a  report  on 
Sand-binding  Grasses 
is  found  in  its  year- 
book for  1898.  Fig. 
86  is  from  this  re- 
port. Such  grasses 
as  are  found  to  thrive 
naturally  on  the 
sand  -  hills  in  some 
localities  are  set  by 
the  hand  of  man  in 
other  regions.  This 
work  has  been  done 
near  San  Francisco, 
along  the  shore  of 
Lake  Michigan,  and  near  Provincetown,  Mass.  The  danger 
in  the  last  case  is  that  the  sands  will  blow  across  a  narrow 


Fig.  87.— a  boulder  resting  on  a  bank  of  shale 
which  is  swept  by  drifting  sand,  protects 
one  spot  while  the  ground  all  about  is  worn 
away ;  northwestern  Arizona. 


WIND  WORK 


117 


neck  of  land  and  fill  up  the  harbor.  Grasses  have  thus 
been  used  to  defend  the  coasts  of  France,  Holland,  and 
Denmark.  Where  no  precaution  is  taken,  a  dune  has  been 
known  to  migrate  as  much  as  70  feet  in  one  year. 


Fig.  88.— Blocks  of  igneous  rock  sculptured  by  wind  driven  sand  ;  Mono  Valley,  Cal. 
The  sand  comes  from  the  right. 


120.  The  sand  blast. — Sand  driven  by  powerful  currents 
of  air  is  used  in  the  arts  for  many  purposes.  Patterns  are 
cut  on  glass,  and  heavy  plate  glass  is  readily  pierced  by  such 
means.  The  blast  is  used  for  bringing  out  the  grain  of 
wood,  for  giving  a  granular  surface  to  iron  and  steel,  for 
carving  inscriptions  on  stone,  for  lithographic  drawing, 
for  cleansing  the  inner  face  of  tanks  from  foreign  deposits, 
and  for  refacing  grindstones  and  emery-wheels. 

Sand  blown  by  natural  winds  does  similar  work,  and 
this  natural  sand  blast  suggested  its  use  by  man.  Wher- 
ever the  wind  habitually  drives  sand  upon  boulders  or 
ledges,  wearing  will  result.  Many  sand-carved  boulders 
have  been   found  in   the  Androscoggin  Valley,  near  the 


118    AN  INTRODUCTION  TO   PHYSICAL   GEOGRAPHY 

White  Mountains.  But  it  is  only  in  dry  regions  that  such 
work  is  important,  and  many  examples  of  it  have  been 
found  in  the  western  United  States  and  the  Sahara.  The 
student  should  not,  however,  suppose  that  this  work  is  to  be 
compared  in  importance  with  that  of  weathering  or  streams 
or  glaciers. 


CHAPTER   VI 

GLACIERS 

Mountain"  Glacieks 

121.  The  Gorner  Glacier. ^Monte  Rosa  is  one  of  the  high- 
est peaks  of  the  Alps.  West  of  it  are  Lyskamm,  Breit- 
horn,  and  the  Matterhorn.  All  these  mountains  rise  to 
ahout  15,000  feet  ahove .  the  sea,  and  are  the  highest 
points  of  a  lofty  ridge  which  marks  the  boundary  of 
Switzerland  and  Italy.  N^orth  of  this  ridge  a  deep  valley 
runs  from  east  to  west,  and  in  this  valley  is  the  Gorner 
Glacier.  For  the  places  noted  in  this  section  the  student 
should  constantly  refer  to  the  map  (Fig.  89).  The  glacier 
fills  the  valley  to  a  depth  of  many  hundred  feet,  and  flows 
from  east  to  west.  It  is  known  at  its  lower  or  northwest 
end  as  the  Boden  Glacier.  At  its  eastern  end,  covering  the 
high  slopes  north  of  Monte  Rosa,  are  great  fields  of  snow. 
This  snow,  accumulating  from  year  to  year  and  from  cen- 
tury to  century,  packs  together,  pushes  down  the  moun- 
tain slopes,  and  within  a  short  distance  becomes  solid  ice, 
which,  at  the  rate  of  a  few  inches  or  feet  per  day,  flows 
westward  down  the  valley.  The  whole  length  of  snow-field 
and  the  glacier  proper  is  nine  miles.  The  upper  edge  of 
the  snow-field  is  nearly  15,000  feet,  and  the  lower  end  of 
the  glacier  is  about  6,000  feet,  above  the  sea. 

The  glacier  is  not  entirely  formed  from  the  snows  at  its 
eastern  end.  Other  snows  gather  on  the  north  slopes  of 
the  ridge  already  described.  These  form  several  smaller 
glaciers  which  join  the  Gorner  Glacier  on  the  south  and 

119 


120    AN  INTRODUCTION  TO   PHYSICAL  GEOGRAPHY 

swell  its  size.  These,  beginning  at  the  east,  are  :  the  Monte 
Eosa,  Grenz,  Twin,  Schwarze,  Breithorn,  Little  Matterhorn, 
and  Theodul  Glaciers.  From  the  ice  and  snows  rise  craggy 
ridges  and  peaks,  which  all  together  form  one  of  the  most 
splendid  views  to  be  found  in  any  land. 

Along  the  trunk  glacier  the  student  will  see  upon  the 
map  a  number  of  brown  lines.  These  usually  lead  up  to  a 
rocky  ridge  which  separates  two  tributary  glaciers.  As  the 
glaciers  crowd  the  mountainside  they  pluck  away  blocks 
of  rock.  Other  waste  rolls  down  the  steep  slope  and  lodges 
on  the  edge  of  the  stream  of  ice.  Such  a  line  of  waste  on 
the  side  of  a  glacier  is  a  Lateral  Moraine.  When  two  glaciers 
unite,  the  left  lateral  moraine  of  the  one  and  the  right 
lateral  moraine  of  the  other  join  together,  and  a  ridge  or 
tract  of  waste  stretches  far  down  the  trunk  glacier.  Such 
are  the  brown  lines  on  the  Gorner  Glacier ;  they  are  called 
Medial  Moraines. 

Where  the  glacier  is  finally  overcome  by  the  melting  of 
its  ice  at  the  lower  end,  in  the  warmer  valley  region,  more 
waste  is  found.  The  stones  carried  on  the  surface  as 
medial  moraines,  and  the  stones  and  finer  waste  carried 
along  in  the  bottom  of  the  glacier,  are  lodged  in  confused 
heaps  where  the  glacier  ends,  and  make  up  the  Terminal 
Moraine. 

Let  the  student  refer  again  to  the  map.  He  will  ob- 
serve streams  which  come  to  an  abrupt  end.  They  are 
formed  by  the  surface-melting  of  the  glacier,  and  plunge 
into  wells  which  penetrate  the  glacier  to  great  depths,  or 
into  equally  deep  cracks,  or  "  crevasses,"  which  may  cross 
the  glacier  for  considerable  distances.  Where  the  ice  passes 
over  a  step  or  sharp  descent  of  its  rocky  floor,  it  is  strained, 
and  many  crevasses  are  formed.  Cracking  and  melting 
combined  will  often  make  a  glacier  surface  so  rough  that  it 
can  not  be  traversed.  Several  surface  pools  are  also  shown. 
It  will  be  readily  understood  that  the  deep  fissures,  wells, 
pools,  and  surface  streams  vary  much  from  time  to  time. 


121 


122     AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


Melting  goes  on  also  within  and  at  the  bottom  of  the 
ice.  All  these  waters  gather  into  a  subglacial  stream, 
which  is  often  a  considerable  river,  and  flows  into  the  open 
air  at  the  lower  end  of  the  glacier.     This  stream  under 

the  glacier  wears  the 
rocks  like  any  other 
stream.  It  also  re- 
ceives much  rock- 
flour  made  by  the 
heavy  grinding  of  the 
ice,  and  has  a  milky- 
white  appearance, 
which  it  retains  for 
many  miles  in  the 
open  valley.  The 
Swiss  call  such  writer 
"glacier  milk. " 
When  firm  rocks  are 
ground  up  the  pow- 
der is  usually  white, 
but  the  powder  from 
weathering  is  yel- 
lowed by  iron  oxid. 
The  lower  end  of 
the  glacier  sometimes  for  a  term  of  years  pushes  farther 
and  farther  down  the  valley ;  and  it  has  thus  destroyed  cot- 
tages which  were  built  too  near  its  foot.  The  cause  of 
such  fluctuations  is  not  well  understood,  but  we  can  see 
that  any  change  of  climate  which  brought  more  snow,  or 
less  heat  for  melting,  would  make  the  glacier  deeper,  and 
cause  the  ice  to  push  into  the  valley  with  more  vigor. 

We  have  thus  studied  the  Gorner  Glacier  with  care,  not 
because  it  is  the  largest  even  of  the  Swiss  ice-streams,  but 
because  it  shows  the  characters  of  a  glacier  in  an  instructive 
way,  and  because  the  features  described  belong  more  or 
less  to  all  glaciers.     For  a  more  complete  knowledge,  refer- 


FiG.  91.— A  crevasse.     See  page  120. 


B-o 


c  2 


aj    o 
03  Ph 

il 


OJ    S 


11 


124    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

ence  should  be  made  to  TyndalFs  Forms  of  Water,  his 
Glaciers  of  the  Alps,  to  text-books  of  geology,  and  to  works 
on  the  Ice  Age.  We  are  now  prepared  to  refer  to  other 
glaciers,  and  to  see  how  important  they  are,  or  have  been, 
upon  the  land  surfaces  of  the  earth. 

122.  Other  Alpine  glaciers. — Switzerland  alone,  not  in- 
cluding the  Austrian  Alps,  has  several  hundred  glaciers. 
Of  these,  138  are  more  than  5  miles  long.  The  Aletsch,  15 
miles  long,  is  the  greatest.  The  Lower  Aar,  10  miles  long, 
was  made  famous  by  the  studies  of  Louis  Agassiz.  The 
Rhone  Glacier,  source  of  the  Rhone  River,  has  a  wonderful 
fall,  or  cascade,  1,600  feet  high,  shown  in  Fig.  250.  At  the 
brink  the  ice  is  rent  by  innumerable  crevasses,  but  at  the 
foot  it  is  welded  again  into  a  compact,  smooth  body. 

123.  Mountain  glaciers  of  other  lands. — In  Europe  these 
are  found  in  the  Pyrenees  and  Caucasus,  and  in  Xorway. 
In  the  last  country  they  often  descend  from  the  uplands 
and  enter  the  sea  at  the  head  of  the  sunken  valleys,  or 
fiords,  which  abound  on  that  coast.  In  Switzerland  no 
glacier  reaches  a  point  less  than  3,000  feet  above  sea-level. 
In  Norway,  as  in  Spitzbergen,  Greenland,  and  other  north- 
ern lands,  the  lowlands  are  not  warm  enough  to  prevent 
the  descent  of  the  ice-streams  to  the  sea. 

In  the  Himalayas  much  longer  and  larger  glaciers 
occur  than  are  found  in  Europe,  though  less  is  known 
and  written  about  them.  Many  glaciers  occupy  the  high 
valleys  and  slopes  of  the  Andes  in  South  America  and  of 
the  mountains  of  New  Zealand.  In  Patagonia  they  de- 
scend to  the  sea. 

124.  Mountain  glaciers  of  North  America. — In  the  United 
States  these  are  all  of  moderate  size  and  lie  in  the  high 
mountains  of  the  West.  Xot  long  ago  a  small  glacier  was 
found  in  the  Rocky  Mountains  west  of  Denver  in  Colorado, 
and  named  the  Arapahoe.  It  is  of  interest  as  a  remnant  of 
the  greater  glaciers  that  once  filled  the  high  valleys  of  that 
State.     Other  and  larger  glaciers  occur  in  the  high  ranges 


r 


Fig.  93.— A  yla(  ier  of  the  Cascade  range  in  northern  Washington.  Though  it  is 
August,  the  higher  parts  are  covered  by  snow  and  there  are  banks  of  snow  farther 
down.  The  lower  end  is  surrounded  by  a  curving  terminal  moraine.  It  is  one  of 
a  series,  each  occupying  an  alcove  which  it  has  helped  to  make,  and  separated 
from  its  neighbors  by  narrow  crests.  The  terminal  moraine  of  another  glacier 
occupies  the  foreground. 

125 


126    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

of  northern  Montana  and  Washington  (see  Fig.  93).  A 
few  are  scattered  among  the  peaks  of  the  Sierra  Nevada, 
and  five  lie  on  the  upper  slopes  of  Mount  Shasta.  Sev- 
eral rivers  which  flow  into  the  Columbia  and  into  Puget 
Sound  have  their  sources  in  the  glaciers  of  Mount  Rainier, 
Mount  Hood,  Mount  Baker,  Mount  Jefferson,  and  Mount 
St.  Helens.  They  are  distinguished  from  other  rivers  of 
the  region  by  the  milkiness  of  their  waters. 

As  we  follow  the  Cordilleran  system  of  mountains  into 
Canada,  we  meet  with  larger  glaciers,  some  of  which  de- 
scend into  the  lower  valleys.  Those  of  the  Selkirk  Moun- 
tains, along  the  line  of  the  Canadian  Pacific  Railway,  are 
best  known.  Going  northward  to  Alaska,  we  find  the  ice- 
streams  still  larger,  and,  like  those  of  Norway  and  Pata- 
gonia, they  often  flow  down  to  the  sea. 

One  of  the  greater  of  these  ice-streams  is  the  Muir 
Glacier  (Fig.  95).  It  is  also  one  of  the  more  accessible, 
and  is  visited  annually  by  steamers  carrying  parties  of 
tourists.  It  lies  near  the  head  of  Glacier  Bay,  from  whose 
waters  its  cliffs  of  gleaming  white  rise  to  a  height  of  200 
feet.  Its  thickness  is  900  feet,  so  that  much  lies  below  the 
water  surface  (Fig.  94).     From  the  cliffs,  masses  crack  off 


Fig.  94.— Section  of  end  of  Muir  Glacier  and  part  of  Glacier  Bay,  showing  icebergs. 
Scale,  1  inch  =  3,500  feet. 


at  intervals  and  float  down  the  waters  of  the  bay  as  small 
icebergs.  On  either  hand  are  mountains  several  thousand 
feet  in  height,  and  one  rocky  mass  protrudes  through  the 
surface  of  the  ice-stream  to  a  height  of  1,500  feet.  At 
least  nine  ice-streams,  flowing  from  interior  valleys,  come 
together  in  a  broader  valley  or  basin  to  form  the  trunk 


10 


128    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

glacier.  This  glacier  was  first  visited  in  1794,  by  Vancouver, 
who  found  it  much  larger  than  it  is  now.  It  was  joined 
with  glaciers  from  other  sides  of  the  bay,  and  for  40  miles 
the  sea  was  displaced  by  a  solid  mass  of  ice. 

On  the  southern  slopes,  and  in  the  deep  valleys  of  the 
range  culminating  in  Mount  St.  Elias,  are  several  large 
glaciers.  These  unite  on  the  narrow  plain  that  separates 
the  mountains  from  the  sea,  and  form  a  glacier  30  miles 
wide  and  extending  70  miles  along  the  base  of  the  range. 
At  some  points  the  sea  is  reached,  and  at  others  a  narrow 
strip  of  land  lies  between  the  glacier  and  the  shore.  Thus 
we  have  mountain  glaciers  at  the  sources,  but  a  Piedmont 
(foot  of  the  mountain)  glacier  below.  This  lower  ice-field 
is  called  the  Malaspina  Glacier.  Its  inner  part,  toward  the 
mountains,  is  clear,  but  the  outer  border,  for  a  width  of 
several  miles,  is  covered  with  rocks  and  earth  brought  in 
the  ice  and  exposed  as  the  ice  melts.  On  parts  of  the 
overlying  earth  thick  forests  are  growing. 

CONTIKEKTAL    GLACIERS 

These  are  more  often  called  Ice  Sheets,  because  they 
spread  widely  over  the  land,  concealing  its  hills  and  val- 
leys. The  ice  sheets  which  now  exist  are  instructive,  be- 
cause they  prove  the  possibility  of  such  gatherings  of  ice  in 
former  times,  and  because  they  throw  light  on  the  behavior 
and  appearance  of  the  ancient  continental  glaciers. 

125.  Greenland  ice-sheet. — The  larger  part  of  this  great 
northern  land  is  covered  with  a  sheet  of  moving  ice.  The 
ice-fields  are  about  1,300  miles  long  from  north  to  south, 
and  from  300  to  600  miles  wide.  Much  of  the  border  of 
the  island  is  free  from  ice,  especially  toward  the  south, 
and  along  this  narrow  rim  of  land  are  the  humble  vil- 
lages of  the  people,  who  live  by  fishing  and  the  hunting 
of  seals  and  walruses.  In  the  interior  the  surface  of  the 
ice-cap,  as  it  is  often  called,  is  several  thousand  feet  above 
sea-level,  and  is  an  even  plain.     Thence  it  slopes  gently 


130    AN   INTRODUCTION  TO   PHYSICAL  GEOGRAPHY 

down  toward  the  edge  of  the  land,  where  it  pours  out 
through  valleys  and  stretches  of  lower  ground  to  the  sea- 
border.  Some  of  the  ice-streams  which  thus  drain  off  the 
great  central  mass  are  very  broad;  the  Humboldt  Glacier 
enters  the  sea  with  a  width  of  about  50  miles.  We  thus 
see  that  whatever  may  be  the  shape  of  the  land  in  the  inte- 
rior of  Greenland,  all  is  shrouded  from  view  by  this  per- 
petual mantle  of  frozen  water.  Nansen  crossed  the  ice  of 
lower  Greenland,  from  sea  to  sea,  in  1888.  In  recent  years 
Peary  has  extensively  traversed  the  ice-fields  of  northern 
Greenland  and  determined  the  limits  of  the  island  toward 
the  pole. 


Fig.  97.— An  iceberg  in  the  North  Atlantic. 

126.  Icebergs. — When  a  Greenland  glacier,  several  hun- 
dred feet  thick,  enters  water  which  is  deep  enough  to  buoy 
it  up,  great  masses  separate  from  the  frontal  part  and  float 
away.  These  are  carried  southward  by  ocean  currents,  often 
as  far  as  the  temperate  latitudes,  where  their  fleets  put  in 
jeopardy  the  summer  navigation  of  the  Xorth  Atlantic. 
The  danger  comes  at  this  season,  because  until  the  late 
spring  the  northern  waters  are  locked  in  ice  which  has 
formed  over  their  surfaces  during  the  winter,  and  the  frag- 


GLACIERS  131 

ments  of  the  glacier  can  get  no  release.  The  thinner  ice 
formed  by  the  freezing  of  sea  water,  and  afterward  drifting 
with  wind  and  current,  is  called  floe-ice.  Even  this  travels 
far  down  into  the  open  sea.  The  Polaris  party  of  about 
twenty  persons,  who  found  themselves  adrift  on  a  floe  in 
October,  1872,  were  picked  up  in  April,  1873,  having  drifted 
for  a  distance  of  2,000  miles. 

127.  Antarctic  ice-fields. — A  sheet  of  ice  much  larger 
than  that  of  Greenland  is  believed  to  occupy  lands  sur- 
rounding the  south  pole.  The  interior  has  never  been  ex- 
plored. Some  navigators  have  coasted  for  long  distances 
in  the  south  seas  along  the  precipitous  edge  of  this  ice- 
sheet,  whose  cliifs  rise  from  100  to  200  feet  above  the  water. 
Expeditions  are  now  setting  forth  from  England,  Scotland, 
Sweden,  and  Germany,  for  the  purpose  of  adding  to  our 
knowledge  of  this  region,  which  is  the  largest  unexplored 
area  yet  remaining  on  the  earth's  surface. 

123.  Conditions  necessary  for  the  formation  of  glaciers. — 
The  Eocky  Mountains  are  as  high  and  cold  as  those  of  the 
Pacific  States,  but  their  glaciers  are  comparatively  few  and 
small.  The  difference  is  due  to  the  abundant  moisture 
and  heavy  snows  of  the  Pacific  belt  and  the  greater  dry- 
ness of  the  mountains  far  from  the  sea.  There  is  a  similar 
contrast  between  interior  Alaska  and  its  southern  border. 
There  are  no  glaciers  upon  the  mainland  of  northeastern 
;N"orth  America,  while  Greenland  is  nearly  covered  with 
ice.  Greenland  is  no  colder,  but  has  more  abundant  snows. 
The  Alps  lift  their  great  ridges  and  peaks  into  high  alti- 
tudes, and  thus  stop  and  cool  the  cloud  moisture  from  the 
hot  Mediterranean  until  it  falls  as  snow.  A  cold  climate 
and  abundant  snowfall  are  thus  essential  to  the  making  of 
glaciers. 

129.  The  glacier's  work. — We  have  seen  that  a  glacier 
tears  away  rocky  material  and  carries  it  to  considerable 
distances.  We  shall  offer  no  explanation  of  the  motion  of 
a  substance  so  brittle  as  ice.     This  is  a  difficult  question, 


132    AN  INTRODUCTION   TO   PHYSICAL   GEOGRAPHY 

and  for  discussions  of  it  the  student  is  referred  to  text- 
books of  geology.  But  no  one  doubts  that  glaciers  move, 
dig  into  the  crust  of  the  earth,  and  carry  stones  and  finer 
waste  a  distance  of  a  few  or  even  of  hundreds  of  miles.  A 
moving,  heavy  body  like  a  glacier  grinds  powerfully  upon 
its  rocky  floor,  until  its  base  becomes  shod  with  stones. 
These  stones  held  by  the  glacier  are  like  tools,  and  they 
both  tear  up  boulders  of  the  bed-rock  and  grind  rocky 
flour  from  its  surfaces.  In  mountain  valleys  the  slopes 
rise  steeply  above  the  glaciers,  and  much  material  falls  on 
the  surface.  The  rocks  carried  on  a^id  in  the  glacier  or 
pushed  at  its  base  lodge  where  the  flnal  melting  takes 
place,  forming  moraines.  The  subglacial  stream  carries 
out  large  amounts  of  the  finer  waste.  We  shall  later  sec 
how  glaciers  mold  the  land  surface  into  various  forms. 

130.  Summary. — A  glacier  is  a  mass  of  moving  ice,  in 
a  valley,  or  widely  spreading  over  the  land.  It  can  be 
formed  only  in  regions  of  considerable  cold  and  large  snow- 
fall. At  the  present  time  glaciers  in  low  latitudes  are 
found  only  at  considerable  heights,  while  those  of  the  polar 
regions  often  descend  to  the  sea.  They  accomplish  many 
changes  upon  the  earth's  surface  by  wearing  the  rocks, 
by  stirring  and  changing  the  soils,  and  by  depositing  their 
loads  in  hills  and  sheets  of  land  waste.  Some  of  these 
changes  we  shall  now  study  more  fully. 

The  Glacial  Period 

131.  Evidences  of  a  continental  glacier  in  the  United 
States  and  Canada. — The  land  waste  and  the  land  surfaces 
of  the  northern  United  States  often  resemble  those  found 
in  a  region  of  present  glaciers.  This  is  so  widely  true  as 
to  show  that  great  glaciers  once  covered  the  face  of  the 
country.  We  are  now  to  study  some  of  the  proofs  of  these 
earlier  glaciers. 

132.  The  drift. — If  we  examine  a  field  in  Maine  or  New 
York,  or  northern  Indiana,  or  Iowa,  we  shall  find  the  stones, 


GLACIERS 


133 


the  soils,  and  the  subsoils  often  consisting  of  different  ma- 
terial from  the  underlying  bed-rock.  Pebbles  and  cobble- 
stones, small  boulders  and  great  ones,  even  to  hundreds  of 
tons  in  weight,  are  scattered  over  the  surface  or  buried  in 
the  finer  waste.  Bed- 
rock like  these  loose 
stones  may  be  found  10, 
20,  50,  or  even  some 
hundreds  of  miles  away. 
In  a  given  place  all 
the  boulders  have  come 
in  about  the  same  di- 
rection from  the  parent 
ledges.  In  Xew  Eng- 
land the  stones  have 
traveled  southeast  or 
south.  In  New  York 
the  direction  is  south 
or  southwest,  and  in 
Iowa  south.  These  are 
"  erratic "  or  strayed 
boulders,  once  moved 
by  a  glacier,  as  the  Ma- 
laspina   Glacier  is  now 

carrying  stones  from  Mount  St.  Elias  to  the  sea-border. 
Many  of  the  stones,  however,  are  like  the  rocks  below,  and 
these  have  been  carried  only  a  short  distance. 

It  was  formerly  thought  that  these  stones  were  brought 
over  the  lands  by  a  great  flood.  But  no  explanation  could 
be  given  of  the  origin  of  such  a  flood,  and  the  fact  was 
quite  overlooked  that  the  boulders  commonly  lie  in  finer, 
clayey  waste,  in  which  coarse  and  fine  are  mixed  without 
order.  If  the  mass  had  been  deposited  by  water,  it  would 
have  been  sorted  into  coarser  and  finer  layers,  as  is  always 
the  case  with  such  deposits.  Such  a  formation  of  clay  and 
stones  packed  in  without  sorting  or  order,  known  as  Till  or 


k 

'^^HMBB 

Ufy 

Fig.  98.— An  ••erratic  "  ;  a  boulder  of  granite, 
about  twenty  feet  across,  carried  from  the 
Sierra  Nevada  to  Mono  Valley  by  an  ancient 
glacier. 


134:    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


Boulder  Clay,  is  one  of  the  best  proofs  that  the  region 
where  it  is  found  has  been  covered  by  a  glacier.  The 
ice    moves    slowly   and   heavily   over   the   country,  plows 

and  grinds  the  bed-rocks, 
and  mixes  rock  waste  of 
various  sizes  and  from  va- 
rious sources. 

There  is  another  ele- 
ment in  the  Drift.  A  gla- 
cier is  always  melting ;  and 
the  water  that  pours  from 
top  to  bottom  of  the  ice, 
or  flows  under  the  ice  and 
out  from  its  front,  carries 
clay,  sand,  and  pebbles, 
which  are  laid  down  in  beds 
or  strata.  Thus  we  have 
the  stratified,  or,  as  it  is 
often  called,  the  "  vrashed  " 
drift. 

133.  Glacial  scratches. — 
Many  of  the  boulders  and 
pebbles  of  the  till  are  found 
to  be  Glaciated,  or  marked 
with  parallel  scratches. 
Often  they  look  as  if  en- 
graved with  a  sharp  needle. 
Sometimes  the  scratches 
are  deep  and  rough.  A 
marked  polish  is  seen  on 
some  stones.  If  we  dig 
through  the  subsoil  to  the  bed-rock,  we  shall  often  find 
the  latter  scratched  in  the  same  way  (see  Fig.  100),  or 
even  deeply  grooved  and  carved  into  flutings  and  mold- 
ings. The  glacier,  shod  with  stones  at  its  base,  drags 
these  over  the  bed-rock,  and  thus  both  the  moving  frag- 


A  bank  of  till  ;  Bangor,  Pa. 


GLACIERS 


135 


ments  and  the  floor  over  which  they  move  are  polished 
and  graven. 


Fig.  100.— Shore  of  Lake  Ontario  at  Pillar  Point.    Storm  waves  have  washed  away 
bouldery  till,  exposing  bed-rock  polished  and  scratched  by  the  continental  gla- 


The  direction  of  the  scratches  corresponds  to  that  in 
which  the  erratic  boulders  have  been  moved,  and  so,  put- 
ting these  and  other  facts  together,  we  have  full  proof  that 
glaciers  have  done  the  work. 

Surface  Forms  due  to  Glaciers 

134.  Kames. — In  'New  England,  in  central  and  western 
JSTew  York,  in  Ohio,  Indiana,  Wisconsin,  and  other  Xorth- 
ern  States  are  found  clusters  of  sand-  and  gravel-hills 
(Fig.  101).  Sometimes  they  are  high  and  have  steep  sides. 
If  we  dig  into  them  we  find  irregular  layers,  generally  of 
sand,  gravel,  or  coarse  stones,     E:xcavations  for  building 


136    AN   INTRODUCTION   TO   PHYSICAL  GEOGRAPHY 

and  road  materials  are  common.     Cemeteries   are  often 
placed  upon  such  hills,  because  they  are  always  perfectly 


Fig.  101.— Karnes  ,  near  North  Acton,  Me. 


Fig.  102.— An  esker;  near  Enl 


drained.     Mount  Hope  Cemetery  at  Rochester,  N.  Y.,  is  a 
case  of  this  kind.     Such  hills  are  called  Karnes,  a  Scotch 


GLACIERS 


137 


term.  Similar  hills  are  now 
being  formed  at  the  wasting 
edge  of  the  Muir  Glacier. 

135.  Eskers. — Long,  nar- 
row ridges  of  sand  and 
gravel  are  sometimes  found. 
Often  they  are  winding,  and 
the  same  ridge  may  he  20 
feet  high  in  one  place  and 
50  feet  in  another.  They 
have  steep  sides,  and  are 
often  bordered  by  swampy 
grounds.  Eoads  are  some- 
times carried  along  their 
crests.  Such  ridges,  of  re- 
markable length,  are  found 
in  Maine.  Others  occur  in 
southern  New  England  and 
New  York.  They  are  called 
Eskers,  an  Irish  term,  and 
are  believed  to  have  been 
made  by  streams  flowing  in 
tunnels  under  the  ice. 

136.  Drumlins. — In  east- 
ern Massachusetts,  in  west- 
ern New  York,  and  in  Wis- 
consin are  many  hills,  made, 
not  of  sand  or  gravel,  but  of 
boulder  clay ;  in  shape  either 
round,  oval,  or  elongated, 
and  everywhere  smooth  and 
outlined  by  simple  curves. 
Fig.  103  shows  a  character- 
istic form.  They  are  called 
Drumlins,  also  an  Irish  term ; 
large  numbers  of  such  hills 


138    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

are  found  in  Ireland.  They  occur  only  in  lands  that  have 
been  modified  by  glaciers,  and  are  believed  to  have  been 
formed  under  the  ice.  Those  of  western  Xew  York  are 
very  long  and  have  narrow  crests ;  they  may  be  seen  from 
the  railways  between  Syracuse  and  Eochester. 

137.  Wash  plains. — The  southern  part  of  Marthas  Vine- 
yard is  a  low  plain  sloping  southward  to  the  sea.  The 
north  part  of  the  island  is  hilly  with  moraine,  and  marks 
the  position  of  the  glacier  front  when  the  ice  overspread 
New  England.  The  plain  was  made  by  the  streams  that 
came  from  beneath  the  ice   as  they  wandered   this  way 


Fig.  104.— a  mountain  spur  smoothed  and  rounded  by  a  glacier  ;  Glacier  Bay,  Alaska. 

and  that  and  dropped  their  load.  Many  such  plains  are 
found  in  the  Northern  States,  and  the  process  of  their 
making  may  be  witnessed  at  the  margins  of  many  glaciers 
of  Alaska, 


GLACIERS  139 

138.  Rounded  and  fluted  rock  hills. — If  a  region  is  marked 
by  deep  valleys  and  high  hills,  and  a  great  glacier  comes 
over  it,  the  overriding  and  grinding  of  the  ice  will  subdue 


Fig.  105.— Tuolnmue  Monument,  a  peak  of  the  Sierra  Nevada,  worn  smooth  by  an 
overriding  glacier. 

the  hilltops  and  hillsides,  scour  away  frail  ridges  and  sharp 
summits,  and  leave  it  a  region  of  oval  crests.  Such  hills 
are  shaped  like  drumlins,  but  are  often  much  higher  and 
steeper,  and,  unlike  the  drumlins,  consist  of  bed-rock,  ex- 
cept the  surface  coating  of  boulder  clay.  They  often  show 
a  somewhat  fluted  surface,  the  fluting  being  parallel  with 
the  longer  axis  of  the  elevation.  The  Adirondack  summits 
(Fig.  130)  and  the  granite  dome  shown  in  Fig.  105  are  ex- 
amples of  glacial  rounding  and  smoothing. 

A  similar  change  is  wrought  in  valleys  which  have 
such  position  that  the  moving  ice  follows  them  lengthwise. 
Projecting  angles  are  pared  away  from  their  walls,  and 
in  time  they  become   smooth-sided  troughs  with  broad- 


140    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

ly  curved  bottoms.     The  walls  of  Seneca  Lake  Valley  (Fig. 
42)  were  smoothed  and  straightened  in  this  way,  and  the 


Fig.  lOu.— Uibbs  Canyon,  a  U-trough  of  the  Sierra  Nevada.     Compare  with  Fig.  107. 

highland  east  of  the  valley  illustrates  the  rounding  of  hill- 
tops by  an  overriding  ice-sheet. 


Pio.  107.— Croes-proflle  of  Gibbs  Canyon  (Fig.  106),  showing  former  glacier,  a  ft  c  is 
the  channel  worn  out  by  the  glacier. .  After  the  glacier  disappeared  the  channel 
was  partly  filled  by  waste  from  the  slopes  above  a  and  c.    Scale,  1  inch  =  1,800  feet. 


GLACIERS 


141 


139.  U-troughs. — Mountain  glaciers  also  mold  their  val- 
leys, giving  them  broad  floors  curving  upward  at  the 
sides  so  that  the  cross  profile  resembles  a  wide  U.  The  U- 
trough  is  as  characteristic  of  ice  work  as  the  V-gorge  is  of 
water  work.  See  Figs.  106  and  107,  and  also  the  view  of 
the  Rhone  Valley  (Fig.  250),  where  the  spoon-like  trough 
once  occupied  and  shaped  by  the  glacier  is  beautifully 
shown. 

140.  Giant  kettles. — We  have  seen  how  the  plunging 
and  swirling  water  of  a  river  drills  holes  in  the  rock  (Sec. 
32).  Pot-holes  are  also  drilled 
by  the  streams  which  drop 
through  wells  from  the  top  to 
the  bottom  of  a  glacier.  Fall- 
ing hundreds  of  feet,  the  streams 
acquire  great  force  and  are  able 
to  excavate  pits  of  astonishing 
size.  At  Cohoes,  N.  Y.,  are  sev- 
eral which  measure  from  10  to 
30  feet  in  diameter,  and  these 
held  ponds  and  swamps  after  the 
glacier  which  made  them  had 
disappeared.  In  clearing  out 
the  swamp  muck  from  one  of 
these,  to  find  firm  foundation 
for  a  mill,  the  skeleton  of  a  fos- 
sil elephant  was  discovered. 

141.  Lake  basins.  —  In  the 
northeastern  United  States  are 
many  thousand  lakes.  Ten  thousand  are  found  in  the  sin- 
gle State  of  Minnesota.  Such  regions  as  the  Adirondacks 
and  eastern  Massachusetts  are  thickly  set  with  them.  Un- 
numbered thousands  are  found  in  the  provinces  of  Canada. 
Almost  without  exception,  these  marked  features  of  the 
landscape  are  due  to  glacial  action  in  some  form.  Wher- 
ever, as  on  Cape  Cod,  great  quantities  of   waste  are  left 


Fig.  108.— Pot-holes  drilled  in  gran- 
ite under  an  ancient  glacier ;  Si- 
erra Nevada. 


Fig.  109.— Shapes  of  valley  and  mountainside  wrought  by  a  glacier, 
crags  were  above  the  ice.    Sierra  Nevada. 

143 


Only  the  high 


GLACIERS 


143 


irregularly  as  moraines,  many  hollows   occur  which  will 
hold  water.     Sometimes  remnants  of  the  wasting  ice-sheet 
have  been  buried  by  the  gravels  of  a  wash-plain.     This  ice, 
melting  out  at  last,  has  left  a  basin.     Many  lakes  with 
steep  rims,  in  the  midst     - 
of  much  glacial  waste, 
are  known  as   Kettle- 
hole  Lakes. 

In  highland  regions, 
plateau  or  mountain, 
the  valleys  were  often 
clogged  with  drift,  and 
parts  of  them  thus 
turned  into  lake  ba- 
sins. Most  of  the  Adi- 
rondack lakes  can  best 
be  explained  in  this 
way. 

Grlaciers  are  so  heavy 
and  move  with  such 
power,  that  they  will 
scoop  out  basins  in  the 
solid  rock.  The  lakes 
shown  in  Figs.  109  and 
110  lie  in  bowls  thus 
hollowed  out  by  glaciers,  as  also  do  some  of  the  Alpine  lakes. 
The  Finger  Lakes  of  western  JS^ew  York  are  partly  to  be 
thus  explained,  and  many  lakes  in  the  highlands  of  Canada 
lie  in  rock  basins  dug  out  by  glaciers.  Even  the  Great 
Lakes  of  the  St.  Lawrence  system  are  believed  to  owe  much 
of  their  depth  to  excavation  by  the  great  ice-sheet. 

HiSTOEY    OF   THE    GlACIAL   PeKIOD 

The  full  story  of  the  ice  invasions  belongs  to  geology, 
but  since  it  is  a  very  late  chapter  in  the  history  of  the 
earth  and  tells  much  of  the  shaping  of  the  present  surface  of 
11 


Fig.  110.— Lake  basin  hollowed  from  the  rock 
by  a  glacier  ;  Rocky  Mountains. 


144    AN  INTRODUCTION  TO  PHYSICAL- GEOGRAPHY 

the  lands,  it  is  important  for  geography  also.  We  have 
just  studied  some  of  the  changes  that  glaciers  cause,  and 
we  shall  understand  them  better  if  we  review,  in  a  con- 
nected way,  the  story  of  the  Glacial  period  in  our  own  con- 
tinent. 

142.  Gatherii^  and  advance  of  the  ice. — At  the  begin- 
ning of  the  period  of  cold,  deep  snows  gathered  and  ice 
was  formed  on  broad  uplands  of  Canada.  As  the  cold  in- 
creased, the  areas  of  ice  formation  grew  larger,  and  the  ice 
also  spread  by  flowing  outward  about  its  edges.  The  ice- 
centers  were  not  among  high  mountains,  but  the  ice  grew 
in  thickness  until,  like  a  mass  of  pitch,  it  was  forced  to 
flow  by  its  own  weight.  It  spread  in  all  directions,  and  the 
south  edge  crept  out  over  what  is  now  the  boundary  of 
Canada  and  invaded  the  region  of  the  United  States.  How 
far  it  reached  can  best  be  understood  by  studying  the  map 
(Fig.  111).  The  line  of  its  extreme  limit,  which  geologists 
have  traced  with  care,  traverses  the  southern  border  of  ^N^ew 
England,  crosses  ^ew  Jersey,  Pennsylvania,  and  southwest- 
ern New  York,  and  then  follows  a  crooked  course  north  of 
the  Ohio  Eiver.  It  nearly  follows  the  Missouri  River  across 
Missouri,  and  then  runs  northwest  through  Nebraska,  the 
Dakotas,  and  Montana.  Much  of  our  Western  mountain 
region,  where  now  a  few  remnant  glaciers  are  found,  was 
covered  with  ice,  continuing  into  the  greater  ice-fields  of 
British  Columbia.  North  of  this  line  are  the  till,  the 
traveled  boulders,  plains  and  hills  of  washed  drift,  abun- 
dant lakes  and  waterfalls,  glacial  scratches,  and  many  other 
signs  of  a  glacier.  South  of  the  line  these  are  absent,  and 
both  the  soil  and  the  land  forms  contrast  with  those  on  the 
north.  The  mantle  of  waste  at  the  south  is  made  almost 
wholly  by  the  decay  of  the  underlying  rocks.  There  are 
no  glacial  scratches,  no  erratic  boulders,  and  few  lakes  or 
waterfalls. 

143.  Glacial  epochs. — As  shown  by  the  map,  the  ice  out- 
line had  different  forms  at  different  times.     The  two  forms 


146    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

there  represented  are  the  ones  best  known,  but  there  were 
many  changes.  Sometimes  the  glacier  melted  off  far  to  the 
north,  and  then  more  snows  came  for  a  long  time,  and  the 
ice  gathered  and  pushed  on  again.  All  this  required  a  long 
period,  as  we  count  time ;  but  the  important  point  for  us 
now  to  grasp  is,  that  the  ice  served  as  a  powerful  plow  or 
scraper  to  stir  the  rocks  and  soils,  move  materials  from 
their  sources,  and  make  over  the  surface  of  the  lands. 

144.  Glacial  lakes. — Let  the  student  trace  on  a  map  the 
line  of  water-parting,  or  the  divide,  that  separates  the  Great 
Lake  drainage  from  the  Mississippi,  Susquehanna,  and 
Hudson  Kiver  systems.  Let  him  also  remember  that  the 
ice  in  the  time  of  its  farthest  flow  to  the  south  passed  con- 
siderably beyond  this  divide.  While  it  was  first  melting 
off,  therefore,  the  waters  flowed  mainly  into  the  Mississippi 
and  Susquehanna  basins.  When  the  glacier  had  melted  off 
in  the  vicinity  of  the  present  Chicago  and  Detroit  to  points 
north  of  the  divide,  the  eastern  region  about  the  Mohawk 
and  St.  Lawrence  valleys  was  still  full  of  ice.  It  will 
readily  be  seen,  therefore,  that  there  were  lakes  gathered 
between  the  divide  on  the  south  and  the  wasting  glacier  on 
the  north.  As  the  ice  melted  farther  back  these  lakes  be- 
came greater  in  size  and  often  changed  much  in  form. 
But  in  time  the  ice  melted  out  of  the  Mohawk  Valley  in 
New  York,  and  the  drainage  of  these  glacial  Great  Lakes 
poured  out  between  the  Adirondacks  and  Catskills  to  the 
Hudson  and  the  sea  (see  Fig.  112).  Still  later,  the  glacier 
melted  out  of  the  St.  Lawrence  Valley,  and  the  Great  Lakes 
came  to  their  present  levels  and  forms.  This  is  a  short 
review  of  the  history,  leaving  out  a  multitude  of  the  lesser 
changes.  But  even  this  short  story  helps  us  to  understand 
two  features  of  the  Great  Lake  region.  One  is  the  old 
lake  beaches  which  are  found,  sometimes  several  hundred 
feet  above  the  present  lakes,  and  at  varying  distances  back 
from  their  shores.  The  other  is  the  flat  lands  of  silty  or 
clayey  soil  found  about  the  edges  of  the  lakes,  as  in  north- 


148    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

western  Ohio  and  southern  Ontario.  They  are  lake  bot- 
toms turned  into  habitable  and  often  most  fertile  lands  by 
the  drawing  down  of  the  lakes. 


Fig.  113.— Smooth  bed  and  bluff  shore  of  ancient  lake ;  near  Lewiston,  N,  Y.    See 
page  146  and  Fig.  112. 

145.  Changes  since  the  disappearance  of  the  ice. — The 

rivers,  the  winds,  and  all  the  processes  of  decay  have  been 
at  work  breaking  down  the  rocks,  accumulating  the  soils, 
and  changing  the  land  forms.  Valley  bottoms  covered  with 
coarse  waste  by  glacial  streams  have  been  mantled  over  with 
the  fine  muds  of  river  flooding.  In  swampy  districts  plants? 
including  their  stems,  leaves,  and  fruits,  have  lodged  and 
decayed,  making  beds  of  black  soil  or  of  peat.  Many  shal- 
low lakes  formed  during  the  glacial  invasion  have  been 
filled  by  such  vegetation,  and  by  fine  muds  brought  in  by 
streams.  The  "vlies"  or  natural  meadows  of  the  Adiron- 
dacks  mark  such  filled  lake  basins,  and  they  can  be  found 
everywhere  in  the  northeastern  United  States. 

Many  lakes  which  remain  have  their  bounds  narrowed 
by  deltas  built  at  their  heads  or  along  their  shores  where 
streams  enter.     A  great  number  of  deep  gorges  have  been 


GLACIERS 


''^y      149 


cut  out  by  streams  since  the  glacial  time.  Reference  was 
made  to  many  of  these  in  Chapter  III.  Here  belong 
Niagara,  Trenton,  Ausable,  and  a  multitude  of  more  local 
fame. 

146.  Changes  in  the  course  of  rivers. — Much  waste  was 
lodged  in  valleys,  either  at  certain  points  or  for  long  dis- 
tances. Hence  rivers  often  could  not  resume  their  ancient 
paths  and  sought  out  new  ones,  following  the  lowest  levels 
they  could  find.  The  Mississippi  was  thus,  as  we  have 
seen,  forced  out  of  its  old,  open  valley,  at  Minneapolis,  and 
is  gradually  reducing  the  grade  of  its  new  course  by  cut- 
ting the  gorge  that  runs  to  Fort  Snelling.  Before  the 
Glacial  period  much  of  western  Pennsylvania  drained  to  a 
valley  where  now  is  Lake  Erie,  and  the  upper  valley  of  the 
Missouri  found  outlet  to  Hudson  Bay  or  the  Gulf  of  St.  Law- 
rence instead  of  to  the  Mississippi  and  the  Gulf  of  Mexico. 

Much  of  the  effective  water  power  of  the  Northern  States 
is  due  to  such  changes.  The  old  valleys  had  low,  graded 
bottoms,  but  blockades  of  drift  made  the  water  flow  across 
at  higher  levels.  In  the  making  of  new  valleys  rocks  were 
encountered,  and  waterfalls  and  rapids  result.  Water  power 
is  most  effective  when,  by  diverting  the  water  for  a  short 
distance  through  a  raceway,  it  can  be  given  a  plunge  of 
some  height.  Just  such  conditions  were  brought  about  by 
the  glacier  at  Lowell,  Fall  River,  Holyoke,  Bellows  Falls, 
Trenton  Falls,  Niagara,  and  in  a  multitude  of  lesser  cases. 
Many  features  of  natural  scenery  in  which  we  most  delight 
have  thus  come  into  existence  by  the  direct  influence  of 
the  ice  invasion. 

147.  Effects  on  soils. — We  have  seen  that  soils  will  de- 
velop by  rock  weathering  and  the  admixture  of  decaying 
plants  over  nearly  all  lands.  The  exceptions  are  slopes  too 
steep  to  retain  waste,  and  areas  too  dry  to  support  plants. 
The  glacier,  however,  affected  soils  in  several  ways.  It 
added  much  to  the  amount  of  available  rock  waste  by 
grinding  material  from  the  rock  surfaces,  and  making  it  so 


150    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

fine  that  it  could  readily  be  dissolved  by  water,  and  so  taken 
up  by  the  rootlets  of  plants.  It  also  stirred  the  old  soils  and 
mixed  them  with  foreign  matter,  often  greatly  enriching 
them.  Limestone  was  often  ground  up  and  pushed  on  to 
mingle  with  the  somewhat  barren  soils  of  a  sandstone  region. 
We  may  refer  here  also  to  certain  other  useful  mate- 
rials of  glacial  origin.  The  most  common  source  of  build- 
ing sands,  of  brick  clays,  and  of  road-making  gravels  is 
in  the  drift.  Multitudes  of  glacial  boulders,  while  a  hin- 
drance to  tillage,  have  been  gathered  into  fences  and  foun- 
dation walls,  and  the  walls  of  the  first  granite  building  in 
the  United  States,  Kings  Chapel  in  Boston,  are  of  dressed 
granite  boulders. 

148.  Effects  on  animals  and  plants. — Botanists  know  that 
plants  are  grouped  largely  according  to  the  nature  of  soils 
and  their  situation.  Swamps  have  their  plant  societies,  as 
also  the  sand-hills,  and  the  clayey  uplands.  Thus,  by  de- 
termining land  forms  and  soil,  the  glaciers  have  influenced 
the  groupings  of  herbs  and  trees,  and  through  these  the 
settlements  and  industries  of  man.  We  must  not  forget 
that  long  before  the  ice  invasion  the  land  was  mantled 
with  plants,  and  was  the  home  of  a  multitude  of  animals 
of  lower  order  than  man.  All  these  had  to  change  their 
home  gradually  as  the  icy  winter  spread  over  the  lands. 
In  such  forced  migration  many  kinds  of  living  things  would 
be  overwhelmed,  and,  when  the  ice  had  gone  and  life  re- 
sumed its  sway  over  the  lands,  the  kinds  and  groupings 
were  different  from  those  that  had  existed  before. 

149.  The  Glacial  period  in  Europe. — All  of  northern 
Europe  was  shrouded  in  ice.  Scandinavia,  the  British 
Islands  as  far  south  as  the  Thames  Valley,  the  North 
and  Baltic  Sea  basins,  northern  Germany  and  northern 
Eussia,  were  occupied,  and  changes  were  wrought  similar 
to  those  in  Xorth  America.  The  glaciers  of  the  Alps  were 
much  greater  than  now,  flowing  out  upon  the  plains  of 
northern  Italy,  northern  Switzerland,  and  southern  Bavaria. 


OHAPTEE   VII 

PLAINS 

All  continents  are  composed  in  part  of  low  and  compar- 
atively level  ground,  and  in  part  of  hills  and  mountains. 
No  sharp  lines  of  separation  can  be  drawn,  but  this  will  be 
best  understood  as  we  study  special  cases. 

Marike  Plaiks 

150.  The  Atlantic  coastal  plain. — Southern  New  Jersey 
is  a  low,  flat  country,  and,  excepting  a  narrow  strip  along 
the  Delaware  Eiver,  slopes  gently  southeastward  to  the  sea. 
It  is  a  sandy  region,  with  sluggish  rivers  and  many  swamps, 
and  is  largely  covered  with  scanty  forest.  If  we  dig  below 
the  surface  we  find  beds  of  sand,  gravel,  and  clay,  not  yet 
bound  into  firm  rock,  and,  like  the  surface,  sloping  gently 
down  to  the  ocean  border,  where  they  are  continuous  with 
beds  of  coarser  and  finer  mud  that  descend  beneath  the 
salt  waters.  In  these  uncemented  rocks  are  shells  and 
other  animal  remains,  which  closely  resemble  those  gather- 
ing on  the  bottom  of  the  sea  at  the  present  time.  Except 
that  it  is  exposed  to  the  air,  has  some  coating  of  soil  and 
plants,  and  has  been  slightly  roughened  by  streams,  south- 
ern New  Jersey  is  like  a  sea  bottom,  and  hence  we  conclude 
that  not  long  ago  in  the  history  of  the  earth  it  was  a  sea 
bottom.     Such  a  belt  of  new  land  we  call  a  Coastal  Plain. 

All  of  Delaware  belongs  to  the  same  plain,  and  also 
much  of  Maryland,  east  and  west  of  Chesapeake  Bay.  The 
plain  includes  eastern,  or  "  Tidewater "  Virginia,  as  far 
west  as  Richmond.     The  same  uncemented  deposits,  con- 

151 


152    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

taining  ocean  shells,  are  found,  and  they  incline,  or  dip, 
gently  toward  the  coast  line.  Many  bluffs  on  the  borders 
of  Chesapeake  Bay  show  these  beds  well.  The  chief  streams 
run  to  the  southeast  in  shallow  valleys,  and  the  low  bordering 
bluffs  are  often  notched  by  the  valleys  of  tributary  streams. 
Between  the  watercourses,  however,  are  blocks  of  flat  coun- 
try, not  traversed  even  by  rivulets  (see  Fig.  44).  The  rain 
which  falls  on  these  surfaces  drains  away  by  underground 
movements.  Roads  and  villages  are  more  often  laid  out 
on  the  interstream  areas  than  in  the  valleys. 


Fig,  114.— The  Atlantic  coastal  plain.    A  rice  and  stock  farm  in  South  Carolina. 

Similar  is  the  Atlantic  Coastal  Plain  in  the  Carolinas 
and  Georgia.  There  it  is  about  100  miles  wide,  and  ex- 
tends as  far  as  Raleigh  and  Columbia.  Washington, 
Philadelphia,  and  Trenton  also  mark  its  western  limit. 
The  tide  enters  the  rivers  nearly  or  quite  to  these  cities. 
Beyond  them  the  country  is  higher  and  rougher  and  the 
streams  flow  more  swiftly.  On  one  side  is  the  plain  with 
its  muds  and  half-cemented  beds  of  sand,  its  navigable 
and  sluggish  streams  and  its  flat  uplands  of  small  eleva- 
tion.    On  the  other  side  are  hard  rocks  with  worn  and 


PLAINS  153 

uneven  surfaces,  rising  gradually  to  the  base  of  the  Ap- 
palachian Mountain  ranges.  This  line,  as  already  men- 
tioned, is  known  to  geographers  as  the  Fall  Line  (see  pages 
65  and  70).  There  are  rapids  in  some  of  the  rivers,  as 
they  pass  from  hard  to  soft  rocks,  and  the  association  of 
water-power  with  the  up-stream  limit  of  navigation  has 
caused  many  cities  and  towns  to  grow  up. 

It  will  be  remembered  that  the  resemblance  of  Chesa- 
peake Bay  to  a  branching  river  was  explained  by  saying 
that  the  Coastal  Plain  had  sunk  down  so  as  to  let  the  sea 
flow  into  the  Susquehanna  Valley.  Because  we  now  point 
out  that  the  plain  is  an  old  sea-bed  which  has  risen,  it  must 
not  be  thought  that  one  fact  contradicts  the  other.  Both 
changes  have  taken  place,  but  at  different  times.  After 
the  plain  had  been  formed  under  the  sea  it  was  lifted  so 
high  that  rivers  dug  deep  valleys  across  it;  then  it  was 
lowered  part  way,  to  the  present  height.  Such  risings  and 
sinkings  have  much  to  do  with  the  shapes  of  coasts  and 
coastal  lands. 

Because  America  was  discovered  from  the  east,  it  was 
natural  that  settlements  should  be  earliest  made  on  the  At- 
lantic border,  and  should  thence  extend  across  the  easily 
traveled  lowlands.  The  tidal  rivers  enabled  boats  to  bring 
the  manufactures  of  England  direct  to  almost  every  plan- 
tation, and  to  receive  in  exchange  the  colonists'  crop  of 
tobacco.  Various  parts  of  the  Atlantic  plain  differ  much 
in  soil  and  climate,  and  hence  in  occupations  and  in  den- 
sity of  population.  Such  deposits  as  underlie  this  belt  do 
not  afford  metals  or  coal,  hence  there  is  no  mining  indus- 
try ;  but  in  New  Jersey  and  elsewhere  they  include  clays 
which  are  much  used  for  pottery  and  brickmaking.  The 
country  nearer  the  shore  is  usually  sandy  and  little  suited 
to  agriculture,  so  that  great  tracts  are  still  clothed  with 
their  original  pine  forests,  as  in  southeastern  ]N"ew  Jersey 
and  eastern  North  Carolina  and  Georgia.  At  the  south, 
lumber,  tar,  and  turpentine   are   important   products   of 


154    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

forest  lands.  Other  parts  of  the  plain,  especially  at  some 
distance  from  the  sea  and  along  the  Fall  Line,  have  richer 
soils,  and  are  farmed  to  great  advantage.  In  them  grow 
the  fruits  and  vegetables  which  supply  the  early  markets 
of  the  great  Atlantic  cities  and  inland  towns.  Such  a  rich 
district  is  found  in  ^N^ew  Jersey,  in  the  narrow  belt  which 
drains  toward  the  Delaware  River  near  Philadelphia.  Here 
the  subsoils  often  hold  deposits  of  marl,  which  is  used  as  a 
fertilizer.  Far  to  the  south,  cotton  is  an  important  crop, 
and  rice  is  grown  on  coastal  lands  and  sea  islands  of  South 
Carolina. 

The  student  should  refer  to  Section  101  for  definition  of 
artesian  wells.  A  coastal  plain  offers  all  the  needed  con- 
ditions— continuous,  gently  sloping  beds,  of  which  some 
are  fine  and  close,  not  allowing  the  easy  passage  of  water, 
and  others  are  porous  and  open.  Hence  the  wells  are  an 
important  source  of  supply  for  the  towns  of  eastern  and 
southern  New  Jersey.  In  such  a  region  pure  surface-waters 
can  not  readily  be  obtained. 

151.  Siberian  marine  plain. — The  largest  plain  in  the 
world  forms  the  north  and  west  parts  of  Siberia.  It  is  dif- 
ficult to  appreciate  the  size  of  Siberia  as  a  whole.  It  has 
been  said  that  if  the  United  States  were  spread  out  upon 
it,  enough  land  would  be  left  to  hold  all  Europe,  save 
Russia,  with  a  space  larger  than  the  German  Empire  yet 
to  spare.  ]N"orth western  Siberia,  to  a  width  of  1,000  miles 
or  more,  is  a  smooth  plain  sloping  imperceptibly  northward 
to  the  borders  of  the  Arctic  Sea.  As  the  rivers  flow  north- 
ward, their  lower  courses  are  often  bound  in  ice  while  their 
upper  parts  are  open,  and  this  leads  to  ice-jams  and  great 
flooding  of  the  plains.  The  divides  between  the  streams 
(Sec.  31)  are  ill-defined  and  variable.  Shallow  lakes  and 
quaking  marshes  are  of  large  extent.  The  water  from  the 
marshes  between  the  Ob  and  Yenisei  flows  sometimes  to 
one  river  and  sometimes  to  the  other,  according  to  the 
direction  of  the  wind.    From  about  the  sixty-ninth  parallel 


PLAINS  155 

northward  the  plain  is  a  Tundra,  or  frozen  prairie.  The 
cold  of  winter  lasts  longer  there  than  the  warmth  of 
summer,  and  controls  the  condition  of  the  ground.  To  a 
great  and  unknown  depth  the  subsoil  is  forever  frozen ;  but 
in  the  brief  summer  the  snows  melt  away  and  a  few  inches 
or  a  few  feet  of  the  soils  are  unlocked  by  the  sun.  Grass, 
mosses,  swamp  plants,  and  stunted  berry  bushes  grow  rap- 
idly, and  this  scanty  vegetation,  with  fish  from  the  rivers, 
supports  the  scattered  and  miserable  population  of  this 
cheerless  region.  A  few  reindeer  constitute  riches,  and 
these,  for  two-thirds  of  the  year,  live  by  pawing  the  snow 
cover  from  the  mosses  of  the  plain. 

The  tundra  of  Siberia  has  half  the  area  of  thje  United 
States.  It  gradually  passes  into  a  vast  forest  zone  lying 
between  the  sixtieth  and  sixty-ninth  parallels.  Much  of 
the  timber  is  already  exhausted,  but  the  hunting  of  fur- 
bearing  animals  is  an  important  industry.  The  forest  belt 
is  temperate  in  climate,  as  is  a  narrow  but  important  zone 
of  good  agricultural  land  lying  to  the  south  of  it.  The 
latter  is  also  rich  in  minerals.  In  western  Siberia  the  plains 
cross  all  the  zones  now  described,  and  embrace  the  hot,  dry 
region  about  the  Aral  and  Caspian  seas. 

This  vast  plain  is  marine,  and  young.  Kot  long  ago,  as 
geologists  count  time,  it  was  sea  bottom,  and  by  gentle  ele- 
vation of  northwestern  Asia  it  has  become  land.  Its  sur- 
face parts  indeed  have  been  somewhat  modified.  Elvers 
wandering  over  its  northern  floors  have  spread  land  waste. 
The  peaty  accumulations  of  swamps  have  gathered  upon 
it,  and  in  the  dry  regions  of  the  south  the  winds  have 
worked  over  the  surface  materials.  But  below  the  thin 
sheets  of  later  deposits  the  beds  are  marine,  and  the  land 
has  never  been  far  above  the  sea-level. 

Lake  Plains 

152.  Red  River  valley. — The  Eed  River  forms  the 
boundary  of    Minnesota    and    North    Dakota,  and  flows 


156    AN  INTRODUCTION  TO   PHYSICAL  GEOGRAMY 

thence  through  Manitoba  to  Lake  Winnipeg.  The  stream 
meanders  in  strong  curves,  and  has  scarcely  sunk  its  chan- 
nel below  the  surface  of  the  land,  which  is  so  flat  that  one 
may  travel  for  miles  without  rising  or  descending  through 
a  vertical  interval  of  20  feet.  Thus  the  valley,  so  called, 
is  a  smooth  plain,  sloping  faintly  toward  the  river,  from 
the  east  in  Minnesota  and  from  the  west  in  IS^orth  Dakota. 
The  soils  are  everywhere  fine  and  rich,  and  bed-rock  is 
nowhere  to  be  found.  The  fields  are  readily  tilled  and 
produce  enormous  quantities  of  wheat,  for  which  the  re- 
gion is  famed. 

The  student  should  now  recall  the  account  of  glacial 
lakes  given  in  Section  144.  As  large  lakes  formerly  cov- 
ered lowlands  of  Ohio  and  New  York,  so  a  vast  lake  lay 
in  the  valley  of  the  Eed  Eiver.  It  had  its  outlet  where 
now  are  Big  Stone  and  Traverse  lakes,  at  the  south  end  of 
the  valley,  and  drained  down  the  valley  of  the  Minnesota 
Eiver.  Its  northern  boundary  was  the  southern  front  of 
the  glacier.  As  the  glacier  melted  off,  the  lake  grew  larger, 
until  it  was  several  hundred  miles  long.  Over  its  bottom 
settled  the  muds  that  came  from  the  glacier  and  the  ad- 
jacent land.  Lake  Winnipeg  is  a  remnant  of  this  greater 
lake,  which  is  called  Lake  Agassiz,  in  honor  of  Louis 
Agassiz,  the  first  to  recognize  the  traces  of  ancient  glaciers 
in  North  America.  When  the  lake  was  largely  drained  off, 
by  the  removal  of  the  glacier,  its  bottom  became  the  Lake 
Plain  we  have  described. 

153.  Great  lake  plains.— The  traveler  on  the  New  York 
Central  Eailroad  crosses  flat  ground  between  Eome  and 
Syracuse.  To  the  south  are  the  bounding  hills.  To  the 
north  stretches  the  plain  (Fig.  115).  It  is  the  bottom  of 
the  older  Lake  Ontario  and  marks  the  time  of  its  outflow 
through  the  Mohawk  Valley.  If  we  could  drain  Lake 
Ontario,  its  present  bottom  would  form  a  similar  but  much 
larger  plain.  Along  the  Eome,  Watertown  and  Ogdensburg 
Railroad,  east  of  Niagara  Falls,  the  Lehigh  and  other  lines 


Fig.  115.— Plain  of  the  old  glacial  lake  of  the  Ontario  basin  ;  east  of  Niagara  River. 
Fig.  112  gives  a  map  of  the  lake,  and  Fig.  113  its  shore. 

157 


158    AN  INTRODUCTION  TO   PHYSICAL  GEOGRAPHY 

east  of  Buffalo,  the  Grand  Trunk  in  southern  Ontario,  and 
various  roads  crossing  northern  Ohio,  the  same  flat  grounds 
stretch  out  for  long  distances.  Whatever  may  have  been 
the  inequalities  of  the  earlier  surfaces,  they  are  subdued 
and  hidden  by  the  covering  of  lake  muds  gained  at  the 
close  of  the  Glacial  period. 

154.  Great  Salt  Lake  plain. — Great   Salt  Lake  has  an 
area  of  about  1,700  square  miles.     It  is  very  shallow,  but 


Fig.  116.— Shores  of  Lake  Bonneville,  near  Garfield,  Utah.  The  water  stood  at 
various  levels,  enabling  the  waves  to  wash  out  shore  terraces  at  different  heights. 
See  Sec.  154  and  Chap.  XIV. 


40  feet  deep  in  its  deepest  parts.  If  it  were  removed, 
the  bottom  would  appear  to  the  eye  as  a  level  plain.  Such 
a  plain  extends  out  from  the  lake  border  for  long  distances, 
particularly  on  the  west  (Fig.  117).  It  is  a  great  floor  of 
fine  sediment,  interrupted  by  mountain  ridges  and  peaks 
which  here  and  there  jut  through  it,  like  islands  from  a 
sea.     This  floor  is  the  bottom  of  an  older  and  greater  lake, 


12 


160    AN   INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

which  was  as  large  as  Lake  Huron,  and  was  more  than 
1,000  feet  deep.  The  principal  proof  of  such  a  lake  is  in 
the  presence  of  shore-lines  on  the  lower  mountain  slopes 
(see  Fig.  116).  The  reason  that  so  large  a  lake  existed  is 
that  the  climate  was  formerly  much  more  moist  in  that 
region ;  but  with  the  change  to  the  present  climate  the  lake 
dried  away,  until  only  Great  Salt  Lake  is  left.  As  evap- 
oration can  remove  only  pure  water,  all  the  mineral  sub- 
stances which  were  dissolved  in  the  greater  lake  remain  in 
the  smaller,  and  its  water  is  a  strong  brine.  The  ancient 
body  of  water  is  known  as  Lake  Bonneville,  having  been 
named  in  honor  of  Captain  Bonneville,  an  early  explorer 
whose  journals  were  afterward  edited  by  Washington  Irving. 
155.  Other  lake  plains. — We  have  now  studied  three 
illustrations  of  level  lands  of  this  kind — one  in  the  East, 
one  in  the  ^N^orthwest,  and  one  in  the  far  West.  In  the 
first  case  large  lakes  still  remain.  In  the  second  case,  as 
also  in  the  third,  a  lake  of  moderate  size  is  left.  Surface 
drainage  has  uncovered  the  Eastern  and  ^Northwestern 
plains,  and  evaporation  has  brought  the  Western  to  light. 
Wherever  a  swamp  or  meadow  is  found  rimmed  about  with 
higher  land,  a  lake  has  probably  existed  and  has  disap- 
peared by  the  filling  of  the  basin  with  mud  or  the  draining 
off  of  its  waters.  Such  small  lake  plains  are  numerous  in 
all  the  region  of  the  ancient  ice-sheet,  and  they  are  often 
found  in  the  high  mountain  valleys  of  the  West. 

EiYEK  Plains 

The  alluvial  plains  of  rivers,  and  their  deltas,  great  and 
small,  must  be  classed  here.  We  readily  see  there  is  no 
sharp  distinction  between  great  river  deltas  and  the  adja- 
cent coastal  marine  plains,  as  where  the  Mississippi  delta 
merges  into  the  other  lowlands  of  our  Gulf  region.  The 
rivers  of  Siberia,  flooding  wide  districts  of  the  marine 
plain  which  they  cross,  illustrate  this  cooperation  of  river 
and  sea  in  shaping  lowland  surfaces. 


PLAINS  161 

156.  Central  valley  of  California. — Eeference  has  already- 
been  made  (Sec.  61)  to  this  region,  but  we  return  to  it  in 
this  connection  as  a  fine  example  of  a  river  plain  made  not 
by  one  but  by  many  streams.  The  numerous  branches  of 
the  trunk  rivers  have  shifted  their  courses  again  and  again, 
and  thus  spread  widely  the  waste  from  the  mountains. 

WOEK-DOWN   PLAIiq^S 

We  have  already  given  an  account  (Sec.  45)  of  the 
gradual  wearing  down  of  a  river  basin  by  the  meander- 
ing of  the  streams  and  the  weathering  of  the  lands  be- 
tween. If  such  wasting  were  continued  long  enough  a 
perfect  plain  would  be  produced.  But  as  the  slopes  be- 
come gentle  the  wasting  becomes  very  slow,  and  it  is  not 
known  that  the  work  has  ever  been  carried  to  completion. 
Because  the  worn-down  plains  are  imperfect,  they  are 
sometimes  called  Pene-plains,  a  word  meaning  "almost 
plains."  The  part  of  the  Hudson  Valley  shown  in  Fig.  9  is 
a  good  example. 

157.  Piedmont  plain. — Bordering  the  Atlantic  Coastal 
Plain  is  a  belt  of  land  originally  high,  which  has  been  re- 
duced to  an  uneven  lowland  by  the  slow  wasting  of  its  rocks. 
Lying  at  the  eastern  foot  of  the  Appalachian  Mountains,  it 
is  called  the  Piedmont  plain.  The  material  it  has  lost  has 
helped  to  build  up  that  part  of  the  sea  bottom  which  is 
now  the  coastal  plain,  and  since  the  uplifting  of  that  plain 
it  has  been  trenched  by  the  rivers  from  the  mountains. 
It  is  further  diversified  by  hills  marking  the  position  of 
rocks  which  have  exceptional  ability  to  resist  the  attacks 
of  storm  and  frost. 

Plaiks  of  Nokth  Amekica 

The  principles  which  have  been  explained  by  reference 
to  a  number  of  scattered  regions  may  now  be  profitably 
applied  to  a  short  study  of  the  lowlands  of  the  interior  of 
our  own  continent.     Let  us  remember  that  North  America 


162    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

is  bordered  on  the  west  and  east  by  great  belts  of  mountain 
and  plateau.  Between  these,  from  the  Arctic  Sea  to  the 
Gulf  of  Mexico,  runs  a  broad  belt  of  lowland,  rising  moder- 
ately on  the  borders  of  Canada  and  the  United  States,  as  in 
Minnesota,  and  sloping  gently  up  to  the  highlands  east 
and  west.     We  shall  now  analyze  this  area  of  plains. 

158.  Gulf  plains.— The  Atlantic  Plain  (Sec.  150)  is  con- 
tinued beyond  Georgia  in  a  marine  coastal  plain,  which 
forms  the  southern  part  of  all  the  Gulf  States,  and  passes 
through  the  Gulf  lowlands  of  Texas  and  down  the  eastern 
side  of  Mexico,  to  the  flat,  hot  plain  between  Vera  Cruz  and 
the  mountains.  Here  is  included  western  Florida,  much  of 
southern  Alabama,  nearly  all  of  Mississippi,  all  of  Louisiana, 
and  a  wide  belt  in  Texas.  Large  parts  of  the  Mississippi 
and  Louisiana  plain  are  directly  shaped  by  the  Mississippi 
River,  and  covered  by  its  flood-plain  and  delta  deposits. 

159.  Prairie  plains. — The  Mississippi  basin  is  floored 
with  old  beds  of  marine  rock,  and  most  of  it  has  never 
been  mountainous  or  raised  to  a  great  height.  In  these 
respects  it  resembles  a  marine  plain,  but  so  much  surface 
rock  has  been  carried  off  by  weathering  and  river  action 
that  no  remnant  of  old  sea  bottom  remains.  It  is  also  true 
that  the  uplifting  of  the  sea  bottom  was  unequal,  and  that 
the  parts  lifted  highest  have  suffered  most  wasting,  so  that 
in  its  broader  features  the  basin  is  a  worn-down  plain.  In 
places  also  it  is  veneered  and  smoothed  over  with  loose 
materials  of  various  origin,  some  deposited  by  glaciers,  some 
by  lakes,  and  some  in  rivers.  Prairie  is  a  French  term, 
chiefly  applied  to  plains  in  Indiana,  Illinois,  Iowa,  Missouri, 
and  to  some  extent  to  bordering  areas,  including  a  strip 
that  on  the  west  extends  southward  into  Texas.  These 
lowlands  are  well  enough  watered  to  bear  luxuriant  native 
grasses  and  cultivated  crops.  They  are  trenched  in  a 
shallow  way  by  many  streams,  and  along  these  most  of  the 
native  timber  is  found.  The  intervening  lands  may  be 
rolling,  but  are  never  high,  and  are  without  forests.     This 


PLAINS 


163 


is  not  because  the  soil  will  not  produce  them,  for  it  is  deep 
and  fertile.  The  absence  of  forest  has  been  ascribed  to 
various  causes,  among  others,  to  the  fires  kindled  by  In- 
dians to  maintain  open  pasturage  for  the  herds  of  buf- 
faloes. Temperate  climate,  rich  soils,  absence  of  forests 
which  must  be  laboriously  cleared,  easy  tillage,  good  grades 
for  railways — such  are  some  of  the  conditions  which  made 
the  settlement  of  the  middle  West  so  rapid,  and  its  growth 
in  wealth  and  population  so  surprising.  Nor  should  we 
forget  that  much  of  the  prairie  surface  has  beneath  it  one 
of  the  most  important  minerals,  coal.  It  may  be  added 
that  the  prairies  merge  often  into  the  lake  plains  about  our 
Great  Lakes,  already  described. 


Fig.  118.— The  Great  Plains  ;  eastern  Colorado.  Note  the  scant  vegetation.  The 
view  includes  a  '"ranch,"  with  trees  and  fields  of  alfalfa,  irrigated  by  a  generous 
spring— a  rare  feature  in  that  dry  region. 


160.  Great  plains. — This  term  includes  a  broad  belt  of 
country  stretching  from  Canada  to  Texas.  The  western 
border  is  at  the  foot  of  the  Eocky  Mountains  in  Montana, 
Wyoming,  Colorado,  and  southward.    On  the  east  it  merges 


164    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

into  the  prairies  in  Dakota,  eastern  Nebraska,  eastern  Kan- 
sas, Oklahoma,  and  Texas.  The  form  of  the  land  is  not 
different  as  we  pass  from  the  prairies  to  the  Great  Plains, 
but  as  a  whole  the  plains  are  drier  and  higher.  The  rise 
in  height,  from  a  few  hundred  feet  on  the  east  to  5,000 
and  6,000  feet  at  the  base  of  the  mountains,  is  gradual. 
The  general  slope  is  so  gentle  that  the  eye  does  not  detect 
the  inclination.  It  must  not  be  thought  that  this  great 
surface  is  a  smooth  plain,  though  large  districts  are  nearly- 
such.     Weathering,  winds,  and  streams  have  made  some 


Fig.  119.— The  Great  Plains,  Kansas.    A  sweet-potato  field  cultivated  by  irrigation. 

parts  very  rough.  It  is  a  plain  as  compared  with  moun- 
tains, and  its  inequalities  are  trivial  in  relation  to  its  great 
size. 

Large  portions  are  old  river  plains  (Fig.  118)  built  like 
the  plain  of  the  central  valley  of  California ;  they  lie  at  the 
west,  between  the  modern  rivers,  which  have  opened  valleys 
at  somewhat  lower  levels.  Farther  east  are  river  plains  built 
by  the  modern  rivers  (Fig.  119).     But  the  greater  part  of 


PLAINS  165 

the  vast  area  is  a  worn-down  plain ;  rocks  which  were  formed 
by  the  sea  or  by  lakes,  and  afterward  lifted  and  bent,  have 
been  exposed  for  ages  to  the  action  of  swinging  rivers,  and 
have  been  pared  away  until  the  grade  is  even  from  the 
mountains  at  the  west  to  the  central  lowland. 

The  Great  Plains  are  interrupted  in  South  Dakota  by 
the  mountainous  group  of  the  Black  Hills.  In  northwest- 
ern ]N"ebraska  and,  Texas  soft  rocks  are  sculptured  into  bad 
lands  (Sec.  82).  In  Kansas,  Colorado,  and  elsewhere,  the 
winds  have  heaped  the  sands,  and  given  diversity  to  the 
surface  (see  Sec.  112).  In  western  Texas  is  the  Llano  Es- 
tacado,  a  nearly  quadrangular,  treeless  tableland,  one-third 
larger  than  the  State  of  New  York,  and  surrounded  by  out- 
ward-facing bluffs.  It  slopes  eastward  a  little  more  than  8 
feet  per  mile,  and  is  exceedingly  smooth. 

161.  Plains  of  Canada  and  Alaska. — The  Great  Plains  of 
the  United  States  are  continued  without  interruption  far 
into  Canada.  On  the  east  are  the  hills  and  ancient  worn- 
down  mountains  of  the  St.  Lawrence  region.  On  the  west 
rise  the  great  mountains  of  the  Cordilleran  system.  Here 
are  the  plains  of  Manitoba,  Assiniboia,  Saskatchewan,  and 
other  provinces.  Wheat  abounds  in  the  southern  provinces, 
and  has  been  grown  as  high  as  latitude  58°,  or  opposite  the 
middle  portion  of  Hudson  Bay.  In  the  Arctic  parts  of  the 
continent  the  plains  resemble  those  of  Siberia,  though  less 
extensive  and  more  broken  by  waters.  The  Yukon  Valley 
and  other  parts  of  Alaska  form  a  tundra  (Fig.  120). 

162.  Summary. — The  student  has  read  this  chapter  to 
little  purpose  if  he  has  not  seen  that  our  object  is  not  the 
mere  description  of  certain  important  plain  lands  in  dif- 
ferent continents.  They  have  been  chosen  in  order  to 
bring  out  the  principles  which  explain  them,  and  which  will 
give  us  the  key  to  other  plains,  like  the  vast,  smooth  low- 
lands of  South  America  or  Australia.  The  way  in  which  a 
plain  was  made  is  one  of  the  most  instructive  things  that 
we  can  learn  about  it.     We  have  seen  that,  with  respect  to 


PLAINS  167 

origin,  plains  are  of  several  classes  :  (1)  Marine  plains,  nar- 
row or  wide,  which  are  sea  bottoms  made  bare  by  uplift ; 
(2)  lake  bottoms,  uncovered  by  draining  away  or  drying 
away  of  the  water ;  (3)  river  lands,  built  of  waste  brought 
and  spread  by  rivers ;  (4)  worn-down  plains,  wrought  out 
by  the  slow  wasting  of  higher  lands.  We  have  also  seen 
that  a  vast  tract  of  plains,  as  in  North  America,  can  only 
be  understood  by  using  all  of  these  principles. 

Still  further,  it  has  appeared  that  plains  having  the 
same  origin  have  different  names  (as  tundra  and  prairie) 
because  they  have  different  climate.  One  region  is  temper- 
ate, another  is  frigid,  and  a  third  is  hot ;  one  is  moist  and 
another  is  dry,  hence  they  differ  in  kind  and  abundance  of 
plants  and  animal  life.  So,  too,  man  himself  is  restricted, 
favored,  and  variously  modified.  The  ways  in  which  the 
surface  of  the  earth  affects  the  life  of  our  race  will  be  spe- 
cially considered  in  Chapter  XVI. 


CHAPTER  YIII 

MOUNTAINS  AND  PLATEAUS 

MouKTAiKS  are  not  an  easy  theme  for  elementary 
study ;  they  are  so  great  and  so  strange  to  many  who 
have  spent  their  lives  on  lowland  plains.  They  are  so 
varied,  also,  that  no  single  definition  can  be  a  good  one. 
We  take  up  first  the  mountains  of  our  own  country,  with 
the  high  plains,  or  plateaus,  that  are  joined  to  them.  Our 
purpose  in  this  is  to  find  the  great  principles  concerning 
all  mountains.  We  wish  to  be  able  to  answer  such  ques- 
tions as  these :  What  is  a  mountain's  form  ?  How  are 
mountains  made  ?  How  are  they  related  to  the  lower  and 
smoother  land  ?  What  is  their  history,  and  how  do  they 
pass  from  youth  to  age,  or  from  high,  sharp  ridges  and 
peaks  to  low,  subdued  hills  ?  How  do  they  affect  the  life 
of  the  earth  ? 

163.  The  Rocky  Mountains  in  Colorado. — As  the  traveler 
approaches  Denver  or  Colorado  Springs  from  the  east,  he 
sees,  rising  on  the  west,  a  lofty  mountain  front,  stretching 
far  away  to  north  and  south.  This  is  the  eastern  face  of 
the  Eocky  Mountains.  The  plains  cease,  and  the  moun- 
tains begin,  at  heights  of  5,000  to  6,000  feet  above  the  level 
of  the  sea.  The  highest  peaks  are  above  14,000,  but  below 
15,000  feet.  Snow  is  always  seen,  even  in  summer,  on  some 
of  the  upper  slopes  and  in  the  high  gorges,  but  the  moun- 
tains by  no  means  appear  to  be  snow-covered,  like  the  Alps, 
whose  heights  are  about  the  same.  Part  way  up  the  Eocky 
Mountain  slopes  timber  grows  (Fig.  121).  The  upper  limit 
is  called  the  Timber  Line.  It  is  not  a  sharp  boundary,  but 
168 


Fig.  121.— South  Lookout  Peak,  13,500  feet  high,  in  the  San  Juan  Mountains  of  Col- 
orado. The  scenery  is  of  the  "  alpine  "  type.  The  fir  timber  extends  to  about 
11,500  feet  altitude. 

169 


170    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

a  belt  along  the  slope,  in  which  the  trees  become  scattering 
and  disappear.  This  may  be  taken  as  a  definition  of  the 
timber-line  for  all  mountains.  Above  this  line  for  several 
thousand  feet,  to  the  top,  are  crags  and  ledges  of  rock, 


Fig.  122.— Summit  of  Pikes  Peak,  Colorado,  14,100  feet  above  eea-level.  There  is 
neither  vegetation  nor  soil.  The  building  is  a  station  of  the  United  States 
Weather  Bureau. 


mostly  granite,  and  great  slopes  of  angular,  sharp-edged 
boulders  riven  from  the  mass  of  the  mountain  by  frosts 
(see  Fig.  122).  The  average  slope  is  not  great.  The  in- 
clined railway  ascends  from  Manitou  to  the  top  of  Pikes 
Peak  at  the  rate  of  about  1,000  feet  per  mile.  The  student 
should  also  remember  that  while  this  mountain  is  more 
than  14,000  feet  above  sea-level,  it  stands  out  but  8,000  feet 
above  the  plains  at  its  foot. 

The  rains  and  melted  snows  from  the  well-watered 
mountain  range  drain  down  to  the  dry  plains  through  deep 
canyons  which  they  have  worn  out  of  the  mountain's  mass. 
Such  are  the  valley  of  Clear  Creek  leading  into  the  moun- 
tains west  of  Denver,  and  the  Cheyenne  and  Fountain 
Creek  canyons,  about  Pikes  Peak.  Stretching  out  from 
the  foot  of  the  range  on  the  east,  are  sheets  of  coarse  waste, 


Fig.  123.— Map  of  the  Rocky  Mountains  in  Colorado.    Scale,  1  inch  =  52  miles. 

171 


172    AN  INTKODUCTION  TO  PHYSICAL  GEOGEAPHY 

sand,  and  gravel.    These  are  deposits  made  by  the  mountain 
torrents  of  present  and  past  times. 

If  we  pass  beyond  this  first,  or  Front  Eange,  we  shall 
enter  a  high,  treeless  plain,  known  as  the  South  Park.  Its 
floor  lies  8,000  feet  or  more  above  the  sea.  It  is  not  a 
valley  worn  out  by  streams  and  weathering,  but  a  region 
left  at  a  lower  level,  while  high  mountains  were  lifted  upon 


i<'iG.  124.— Estes  Park,  Colorado  ;  an  open  prairie  valley,  fringed  with  pines,  and  sur- 
rounded by  ranges  of  the  Rocky  Mountains.    Altitude,  7,000  feet. 

the  east  and  west.  The  climate  is  cool ;  the  Park  is  good 
for  grass  and  grazing,  but  not  for  grain  or  fruit.  West  of 
South  Park  is  the  Mosquito  Eange,  a  great  mountain  ridge 
parallel  to  the  Front  Eange. 

If  we  go  north  in  Colorado,  we  shall  see  that  between 
the  Front  Eange  on  the  east  and  the  Park  Eange  on  the 
west  lie  the  Middle  and  North   Parks,  which  are  broad. 


MOUNTAINS  AND   PLATEAUS  173 

high  valleys  like  South  Park.  The  Mosquito  Eange  may- 
be considered  as  continuing  north  into  the  Park  Eange, 
and  thus  we  have  two  lines  of  mountains  enclosing  between 
them  the  three  parks.  We  should  think  of  each  range  as  a 
tangled  belt  of  high  land,  whose  ragged  offshoots  separate 
the  parks  from  each  other. 

If  we  go  west  instead  of  north,  we  find  the  Sawatch 
Eange  beyond  the  Mosquito,  with  the  upper  valley  of  the 
Arkansas  Eiver  between.  The  Sawatch  here  forms  the 
divide  between  the  Mississippi  and  Colorado  river  systems. 
Still  west  of  the  Sawatch  Eange  are  great  knots  of  high 
peaks,  the  Elk  and  San  Juan  Mountains.  In  southern 
Colorado,  the  Front  and  other  ranges  break  into  different 
arrangements,  and  are  called  by  other  names. 

The  important  fact  is  that  we  have  here  a  chain  of 
mountain  ranges,  running  roughly  north  and  south,  with 
intervening  plains  and  valleys.  The  system  is  complex, 
somewhat  like  the  tangled  and  frayed  strands  of  an  un- 
twisted rope. 

The  Eocky  Mountains  are  lower  and  less  important  in 
central  Wyoming,  but  rise  to  great  heights  and  are  strongly 
developed  in  northern  Wyoming  and  Montana.  Their 
southward  continuation  in  New  Mexico  is  somewhat  lower, 
and  bears  various  local  names. 

164.  Structure  of  the  Rocky  Mountains. — In  order  to  un- 
derstand these  and  many  other  mountains  the  student 
should  refer  to  the  two  great  classes  of  rocks  already  de- 
scribed (page  5).  The  central  and  higher  parts  of  each 
Eocky  Mountain  range  consist  of  the  crystalline,  or  older 
rocks.  ■  On  the  slopes — sometimes  far  up,  but  generally 
near  the  base — and  among  the  foot-hills,  the  stratified 
rocks  are  found.  This  will  be  best  understood  by  reference 
to  Fig.  125.  It  will  be  seen  that  the  Great  Plains  strata 
are  nearly  horizontal,  and  turn  up  at  large  angles  against 
the  foot  of  the  range  on  the  east.  These  upturned  edges 
are  often  a  few  hundred  feet  in  height  above  the  plains. 


174    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

In  the  same  manner  the  beds  on  the  west  side  of  each  range, 
in  the  Parks,  or  on  the  Pacific  side,  are  bent  up.  All  below 
and  between  is  granite  or  some  other  crystalline  rock.  It 
is  for  the  text-books  of  geology  to  seek  to  explain  how  the 
mountains  are  thus  made.     We  can  offer  here  only  the  gen- 

Front  Range 

Great  Plains 


Fig.  125.— Section  to  show  the  arrangement  given  to  the  rocks  by  the  uplifting  of 
the  Rocky  Mountains.  The  base-line  corresponds  to  sea-level.  Altitudes  :  in 
Middle  Park,  8,000  feet ;  crest  of  mountain,  13,500  feet ;  at  the  edge  of  the 
Plains,  5,500  feet. 

eral  explanation  that  great  crushing  has  taken  place,  by 
which  the  once  horizontal  beds  are  bent  up  at  various 
angles,  and  the  older  rocks  were  forced  up  between  them. 
Each  range  is  a  part  of  the  earth's  crust  that  has  been 
raised  high  up,  and  each  great  valley  is  a  part  that  has  been 
less  lifted. 

But  crushing  and  uplifting  tell  only  half  the  story.  The 
lifting  took  place  a  long  time  ago,  and  a  vast  amount  of 
rock  has  been  worn  away.  Xot  only  have  the  mountain 
ridges  been  reduced  in  height,  they  have  been  carved  into 
new  shapes.  Their  gorges  and  spurs,  cliffs  and  peaks,  all 
the  details  that  give  character  to  their  scenery,  are  the 
work  of  storm,  stream,  and  glacier. 

Plateaus  and  Mountains  between  the  Rocky  Moun- 
tai:n^s  and  the  Pacific  Ocean 

165.  The  Colorado  plateaus. — The  Colorado  canyons  have 
already  been  described  (page  71).  We  now  come  to  the 
plateaus  beneath  whose  surfaces  the  gorges  have  been  sunk. 
They  are  not  all  at  one  level,  but  differ  much  in  height 
above  the  sea.  Most  of  western  Colorado  and  eastern  Utah 
and  much  of  Kew  Mexico  and  Arizona  are  included.  This 
great  area  is  limited  by  the  Rocky  Mountains  on  the  east, 
by  the  Wasatch  Mountains  on  the  west,  and  by  the  Uinta 


MOUNTAINS  AND  PLATEAUS 


175 


Mountains  on  the  north.     The  various  tables  are  divided 
from  one  another  by  deep  gorges,  or  are  arranged  liJie  steps, 

each     overlooking     its  

lower  neighbor  from 
the  top  of  a  cliff.  The 
rocks  are  stratified  and 
mostly  horizontal ;  they 
constitute  a  system  of 
great  blocks,  separated 
by  fissures  and  dislo- 
cated so  as  to  stand  at 
different  heights.  Much 
of  the  region  is  a  desert 
because  it  is  so  dry. 
Some  of  the  higher  plat- 
forms receive  enough 
rain  to  create  rich  cov- 
erings of  grass  and  for- 
est. 

166.  Wasatch  Moun- 
tains and  the  Great  Basin. 
—The  Wasatch  Moun- 
tains form  a  short  north  and  south  range  in  central  Utah. 
On  the  east  are  the  Colorado  plateaus.  On  the  west  is 
the  Great  Basin,  so  called  because  it  has  no  outlet  to  the 
sea.  It  is  very  dry  and  its  scanty  waters  enter  lakes,  of 
which  Great  Salt  Lake  is  the  principal  one.  Its  floor  in 
Utah  and  much  of  Nevada  is  4,000  to  5,000  feet  above 
the  sea.  It  would  therefore  be  proper  to  call  it  a  plateau, 
at  least  its  northern  parts.  To  the  south  it  descends, 
and  in  Death  Valley,  southern  California,  is  even  below 
the  sea-level.  Parts  of  the  Great  Basin  are  smooth  as  a 
floor,  but  this  is  not  its  general  character.  Many  moun- 
tain ridges  of  moderate  size  run  far  to  north  and  south 
within  it.  Each  of  these  originated  by  the  uplifting  of  a 
dislocated  block  or  strip  of  the  earth's  crust,  and  usually 
13 


FiQ.  126.— Bird's-eye  view  of  plateaus  in  south- 
ern Utah. 


176    AN  INTRODUCTION   TO  PHYSICAL  GEOGRAPHY 

the  mass  was  tipped  toward  one  side,  so  as  to  give  tliat 
side  a  comparatively  gentle  slope  and  make  the  opposite  one 
a  bold  cliff  (see  Fig.  128).  After  uplift  came  weathering 
and  the  carving  of  gorges.  The  waste  from  the  mountains 
has  not  been  carried  to  the  sea  but  has  gathered  in  the 
valleys  between  the  ranges,  giving  them  smooth  floors  and 
hiding  the  rocks  beneath.     Along  each  mountainside  are 

White  House  Range  ^^.^^^^ 


Fig.  127.— Section  of  the  House  Range  (Fig.  128).  Scale,  1  inch  =  7  miles.  Each  bed 
—for  example,  No.  /i— was  once  continuous  from  side  to  side  ;  but  the  country 
is  now  divided  into  blocks  which  stand  at  different  heights.  Block  B  is  lifted 
higher  than  any  other,  and  its  top  has  been  worn  away,  so  that  all  of  beds  6  and 
5,  and  parts  of  U  and  3,  are  gone.  The  waste  is  gathered  in  the  valleys  at  the 
sides,  where  it  rests  on  and  conceals  blocks  A  and  E. 

series  of  gorge-mouths,  from  which  spread  great  fans  of 
waste,  and  the  fans  usually  merge  together,  giving  to  the 
mountain  a  sloping  foot-plain.  The  Great  Basin  is  limited, 
north  and  south,  by  regions  drained  by  the  Columbia  and 
Colorado  Rivers,  but  the  district  of  block-like  mountains 
and  waste-filled  valleys  extends  beyond  its  boundaries  in 
both  directions. 

West  of  the  Great  Basin  there  rises  in  eastern  Califor- 
nia the  lofty  Sierra  Nevada.  Not  only  do  its  principal 
peaks  surpass  those  of  the  Rocky  Mountains  by  several 
hundred  feet,  but  its  flanks  descend  to  low  valleys  instead 
of  high  plateaus.  It  is  a  superlative  mountain  range,  at 
once  broader,  higher  above  its  base,  and  longer,  than  any 
other  single  range  of  our  domain.  Like  the  ridges  of  the 
Great  Basin,  it  has  been  uplifted  bodily,  the  east  side  most, 
so  that  its  broad  back  drains  to  the  great  California  Valley. 

167.  General  view  of  our  Western  highlands. — The  Rocky 
Mountains,  the  Wasatch,  the  Basin  Ranges,  the  Sierra  and 
the  Coast  Range,  form  the  mountain  uplands.     They  all 


178    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

have  a  general  north  and  south  direction,  but  run  out  or 
change  into  other  forms  with  different  names  as  we  go 
northward  or  southward  to  the  borders  of  the  United  States. 
Beyond,  to  the  north,  they  form  the  mountain  system  of 
British  Columbia  and  Alaska.  Southward  they  continue 
to  the  Isthmus  of  Panama,  or,  in  a  broader  sense,  to  Cape 
Horn.  As  a  whole  they  are  the  Cordillera  of  America. 
All  western  America  is  a  region  of  mountainous  foldings 
and  uplifts  of  the  earth's  crust. 


Fig.  129.— Map  of  parts  of  California,  Nevada,  and  Ltah,  showing  the  Sierra  Nevada 
and  mountain  ranges  of  the  Great  Basin.  Scale,  1  inch  =  275  miles.  Copyrighted 
by  E.  E.  Howell. 

Between  and  adjoining  these  ranges  in  the  United 
States  are  great  plateaus.  The  Great  Plains  are  properly 
also  a  plateau ;  then  come  those  of  the  Colorado  and  Great 
Basin.  As  a  whole,  therefore,  the  western  United  States  is 
a  platform  2,000  to  8,000  feet  high,  carrying  upon  and  above 
it  lofty  ranges  of  mountains.  The  plateaus  are  such  by  up- 
lift from  the  sea-level,  and  the  mountains  are  mountains  by 
reason  of  breaking  and  folding  as  well  as  uplift.     Some 


MOUNTAINS  AND  PLATEAUS  179 

ranges  are  much  older  than  others.  A  single  range  did  not 
come  up  suddenly  to  its  full  height,  but  rose  slowly  and  at 
different  periods.  Uplift,  dislocation  of  the  rocks,  folding 
of  the  rocks,  and  the  close  association  of  plateaus  and 
mountains — such  are  some  of  the  principles  we  have  gained 
from  our  study  thus  far.  We  have  also  learned  that  after 
their  uplift,  mountains  are  greatly  changed  by  down-wear. 
Sharp  peaks,  rough  crags,  rugged  slopes  of  waste,  deep 
gorges,  swift  torrents,  and  broad  foot-hills  and  waste 
plains — such  are  some  of  the  characteristics  of  mountain 
lands. 

168.  Mountains  of  the  eastern  United  States. — These  are 
called  the  Appalachian  Mountain  System  and  extend  from 
near  the  Gulf  to  New  England  and  beyond.  They  are  not 
all  alike  and  they  were  not  all  made  at  one  time.  Let  us 
study  some  of  the  groups  or  chains  which  make  up  the 
system. 

169.  Adirondacks. — These  are  a  small  group  of  ridges 
and  peaks  in  northern  New  York.  The  ridges  are  irregular, 
but  in  general  run  from  northeast  to  southwest.  They  are 
low  mountains,  the  highest  peak  rising  to  little  more  than 
5,000  feet.  For  the  most  part  the  slopes  are  not  steep  and 
are  wooded.  Here  and  there  rocky  heights  rise  above  the 
forest,  but  most  of  the  summits  are  smooth  and  tree-covered. 
They  are  much  older  than  any  of  the  mountains  of  western 
America.  They  may  once  have  been  just  as  high,  but  have 
wasted  to  their  present  form  and  height.  Thus  we  have 
another  illustration  of  the  maturing  and  aging  of  the 
forms  of  the  land. 

170.  Folded  Appalachian  mountains. — The  Adirondack 
Mountains  are  of  crystalline  rock.  So  are  the  highlands  of 
the  Hudson,  and  the  Blue  Eidge,  overlooking  the  Pied- 
mont plain.  But  the  low  mountain  ridges  northwest  of 
the  Blue  Eidge  and  running  through  central  Pennsylvania, 
Virginia,  eastern  Tennessee,  and  far  into  Alabama,  consist 
of  stratified  rocks  built  into  great  folds.     The  rocks  were 


MOUNTAINS  AND  PLATEAUS  181 

once  horizontal,  but  have  been  pushed  into  a  series  of  folds 
or  arches  (Fig.  131).  It  is  such  a  series  of  folds  as  is  made 
by  the  wrinkling  of  a  coat-sleeve.  Or,  grasp  a  thin  stack 
of  writing  paper  on  each  edge  and  push  the  hands  toward 
each  other;  the  sheets  of  paper  will  represent  the  rock 
strata  and  the  pushing  shows  how  the  force  is  applied  in 
making  many  mountains.  In  the  Appalachian  belt  the 
direction  of  the  pushing  was  northwest  and  southeast,  and 
the  wrinkles  run  northeast  and  southwest.  The  wrinkling 
was  very  long  ago,  and  there  has  since  been  an  enormous 
wasting  of  the  rocks.  Some  rocks  have  wasted  more  than 
others,  and  the  ridges  which  are  left  are  not  the  original 
wrinkles,  but  the  projecting  edges  of  such  rock  beds  as 
were  best  able  to  resist  wasting  influences.  These  ridges 
have  already  been  mentioned  in  Section  51,  and  some  of 
them  are  shown  in  Fig.  46.     In  some  of  the  down-folds,  or 

Warrior  Ridge 
Nicholas  ML  ^  - ^ 


Fig.  131.— Section  across  Appalachian  ridges  in  Maryland,  showing  their  relations 
to  the  up-folds  and  down-folds  of  the  rocks.  Parts  indicated  by  the  broken 
lines  have  been  worn  away.    Scale,  1  inch  =  7,000  feet. 

inverted  arches,  of  these  bent  strata  lie  the  coal-beds  of 
eastern  Pennsylvania,  as  about  Scranton,  Wilkesbarre,  and 
Pottsville. 

171.  Mountains  of  New  England.— All  the  mountains  of 
the  New  England  States  are  old  and  subdued,  only  the 
Green  and  White  Mountains  retaining  any  ruggedness. 
In  eastern  Massachusetts,  in  Ehode  Island,  and  Connecti- 
cut, and  on  Manhattan  Island,  the  rocks  show  all  those 
wrinklings  and  complications  which  belong  to  mountains, 
but  the  land  is  a  worn-down  plain.  The  mountains  which 
once  were  there  have  wasted  away  almost  to  the  level  of 
the  sea. 


182    AN  INTRODUCTION   TO   PHYSICAL  GEOGRAPHY 

172.  Young,  mature,  and  old  mountains. — This  is  the  his- 
tory of  mountains :  First,  ridges  are  uplifted ;  they  may  be 
wrinkles  (Fig.  131),  or  they  may  be  blocks,  broken  loose  and 
pushed  upward  (Fig.  127).  In  youth  they  are  small,  in  ma- 
turity large,  but  the  change  is  always  slow.  As  they  grow, 
storm,  frost,  and  stream  attack  them ;  gorges  furrow  them 
from  summit  to  base ;  spurs,  sharp  crests,  and  peaks  are 
carved  out.  Uplift  strives  to  make  the  summits  higher, 
wasting  to  make  them  lower.  The  mountains  are  now  ma- 
ture. When  uplift  ceases,  wasting  continues  alone.  Slowly 
through  the  ages  the  tops  are  lowered,  and  the  rugged 
angles  of  vigorous  middle  life  are  replaced  by  the  smooth 
curves  of  old  age.  The  old  summit  lines  are  now  lost,  and 
new  summit  lines  follow  the  harder  rocks.  Still  more 
slowly  these  too  fade  away,  and  all  that  remains  is  a  worn- 
down  plain,  with  low,  scattered  hills — the  second  childhood 
of  mountains. 

173.  The  Alleghany  plateau. — We  have  seen  that  our 
Western  mountains  either  overlook  or  stand  upon  lofty  pla- 
teaus. In  the  East,  however,  the  plateau  belt,  which  is  asso- 
ciated with  the  Appalachian  Mountains,  is  for  the  greater 
part  as  high  as  the  mountains  themselves.  In  the  long 
wasting  the  steep-sided  mountains  have  suffered  more  than 
the  flat  plateau.  The  plateau  has  its  northeastern  begin- 
ning on  the  west  of  the  Hudson  Eiver,  and  is  known  there 
as  the  Catskill  Mountains.  The  uplands  are  not  mountains, 
in  the  sense  of  being  due  to  folding  and  breaking,  but  are 
like  the  buttes  and  bad-land  hills  of  the  West,  in  having 
their  strata  horizontal.  The  worn  edges  of  the  rock  beds 
form  a  wall,  or  high  cliff,  facing  the  Hudson  Valley  (Fig.  9). 
But  the  tops  of  the  so-called  Catskill  Mountains  are  roll- 
ing and  covered  with  forests  and  meadows,  and,  while  the 
surface  descends  somewhat  to  the  west,  it  passes  gently 
into  the  upland  that  occupies  most  of  central  New  York 
and  all  of  the  southern  part  of  the  State.  This  upland 
is  usually  about  2,000  feet  above  the  level  of  the  sea,  and 


MOUNTAINS  AND  PLATEAUS 


183 


below  its  surface  are   sunk   the   north  and  south  valleys 
which  furnish  the  natural  highways  of  the  region. 

The  same  highland  continues  into  Pennsylvania,  and 
forms  the  northwestern  half  of  the  State.  The  so-called 
Alleghany  Mountains  are  not  true  mountains,  but  are  the 
cliff  or  escarpment  by  which  the  plateau  is  bordered  on  the 
southeast,  and  are  thus  similar  to  the  Catskills.  Beyond 
this,  the  folded  rocks  begin,  but  the  plateau  is  as  high  as 
the  mountains.  Some  of  the  horizontal  beds  of  this  pla- 
teau consist  of  soft  coal, 
and  the  edges  of  the 
coal-beds  are  exposed  on 
the  sides  of  the  valleys, 
as  the  Monongahela, 
south  of  Pittsburg. 

In  other  parts,  espe- 
cially  in   northwestern 
Pennsylvania,      porous 
sandstone  beds  at  some 
distance  below  the  sur- 
face,   contain    mineral 
oil,  or  petroleum,  and 
natural     gas.        These 
products     are     lighter 
than  water,  and  would 
long    ago     have    risen 
through  the  rocks   and 
close,   fine-grained   beds 
sands,"  and  keep  the  oil 
boring.      Much   of  the 


Fig.  132.— a  bed  of  bituminous  coal— "the 
Pittsburg  coal  "—with  strata  of  shale  and 
sandstone  above  and  below. 


been  lost,  but  for  the  fact  that 
overlie  the  porous  beds  or  "oil 
(or  gas)  down.  It  is  reached  by 
petroleum  is  refined,  producing 
illuminating  oil  and  many  other  useful  substances.  The 
refineries  are  in  the  oil  region,  and  also  in  the  cities  of  the 
seaboard,  to  which  the  crude  oil  is  pumped  by  means  of 
pipe-lines  hundreds  of  miles  in  length. 

The  plateau,  with  its  deposits  of  oil  and  coal,  continues 
through  Virginia,  Kentucky,  and  Tennessee,  where  it  is 


Fig.  133.-  I'i. .:-!:.. -  :.:.u  j...jys  about  Chattanooga,  Tenn.  Scale,  1  inch  =  7  miles. 
The  uplands  are  parts  of  the  Gumberlaud  plateau.  The  main  plateau  is  seen  at 
the  extreme  northwest.  A  detached  portion,  the  Walden  plateau,  crosses  the 
map  from  northeast  to  southwest,  and  the  end  of  Lookout  Mountain  shows  at 
the  south.    Gorges  are  carved  in  all  these  uplands. 

184 


MOUNTAINS  AND  PLATEAUS  185 

known  as  the  Cumberland  Plateau.  There,  as  farther 
north,  it  is  a  flat,  high  country,  with  a  cliff  overlooking 
the  mountain  ridges  and  valleys  on  the  east.  On  the  west 
it  slopes  gradually  down  toward  the  prairies  and  low  plains 
of  the  Mississippi  Valley,  resembling,  in  this  respect,  the 
Great  Plains  west  of  the  river.  Far  to  the  south  it  is 
divided  into  belt-like  parts  by  straight,  open  valleys  (see 
Fig.  133). 

174.  Mountains  of  other  lands. — We  may  describe  the 
geography  of  mountains  by  comparing  a  few  other  ex- 
amples with  those  of  North  America.  The  highlands  of 
Scotland  are  like  the  Adirondacks  and  the  uplands  of  Xew 
England  in  being  very  old  mountains,  much  subdued  and 
of  small  height.  Similar  are  the  mountains  of  the  English 
Lake  District  in  the  north  of  England,  whose  chief  sum- 
mits are  little  more  than  3,000  feet  above  sea-level.  The 
mountains  of  the  Scandinavian  peninsula  are  also  old  and 
worn,  though  higher  than  those  of  Great  Britain. 

In  the  south  of  Europe,  however,  we  find  mature  moun- 
tains, high  and  very  rugged.  In  the  Pyrenees  and  the 
Alps,  both  the  unstratified  and  the  stratified  rocks  have 
vbeen  squeezed,  folded  and  broken,  and  forced  upward,  so 
that  the  mountains  rise  from  twelve  to  nearly  sixteen  thou- 
sand feet  above  the  sea.  As  they  were  not  overridden  by 
the  ice  of  the  glacial  period,  their  peaks  are  unworn  ;  and 
the  gnawing  of  the  modern  glaciers,  which  flourish  in  al- 
coves under  their  summits,  keeps  their  crests  blade-like. 
Below  the  glaciers,  torrents  are  powerful  and  busy,  and  in 
all  the  uplifted  country  are  gorges  and  deep  valleys.  Sharp 
peaks,  lofty  and  often  vertical  cliffs,  and  valleys  strewn 
with  the  waste  of  the  heights,  are  the  features  of  the  land. 
Conspicuous  in  the  scenery  of  the  Alps  are  its  separated 
peaks,  springing  from  spurs  between  gorges  and  standing 
free  from  the  main  crest-line.  These  are  often  named 
needles  or  horns,  as  in  the  Matterhorn  (stag-horn),  shown 
in  Fig.  134.     A  line  of  peaks  marks  a  ridge,  a  strand  of 


jp^"^ 

k. 

^  1 

1 

Fig.  134.— The  Matterhorn.    See  page  185. 


186 


MOUNTAINS  AND   PLATEAUS  187 

ridges  makes  a  chain,  and  several  chains,  as  in  western 
America,  make  up  a  mountain  system.  On  the  north  of 
the  eastern  Alps  is  the  Bavarian  plateau,  with  a  smooth 
surface  about  2,000  feet  above  the  sea.  Munich  stands  on 
this  plateau  near  the  northern  foot  of  the  mountains,  and 
the  Danube  flows  eastward  over  it.  It  is  related  to  the  Alps 
as  the  Great  Plains  are  to  the  Eocky  Mountains. 

In  Asia,  the  highest  mountains  in  the  world,  the  Hima- 
laya, are  in  middle  life,  like  the  Alps.  Far  up  among 
their  heights  the  rocks  contain  shells  which  originally  grew 
in  the  sea.  Along  a  belt  running  far  east  and  west,  the 
earth's  crust  was  crumpled  and  broken  and  the  mountains 
reared.  Glaciers,  deep  valleys,  and  strong  streams  are  com- 
mon here  as  in  the  Alps.  In  both  regions  immense  land- 
slides occur,  as  ill-supported  sides  of  the  mountain  fall  oif 
into  the  valleys.  In  both,  also,  snow  comes  down  in  the 
form  of  avalanches,  overwhelming  forests  and  destroying 
human  life. 

To  the  north  is  the  plateau  of  central  Asia.  Its  highest 
parts  in  Tibet  are  about  14,000  feet  above  the  sea,  or  as 
high  as  our  western  mountain  peaks.  Hence  the  region  is 
sometimes  called  the  "  Eoof  of  the  World."  As  our  Great 
Basin  plateau  is  broken  by  mountains,  so  is  the  plateau  of 
central  Asia,  and  its  mountains  and  plains  are  on  a  grander 
scale.  Gradually  on  the  north,  plateau  and  mountains  de- 
scend to  the  level  of  the  Siberian  plains.  A  vast  continen- 
tal rise  of  land,  of  which  the  rugged  parts  are  mountains 
and  the  smoother,  intervening  parts  are  waste-floored  plains 
^such  is  the  character  of  the  highlands  of  Asia,  as  of  those 
of  western  America. 

The  Andes  also  are  high  and  rugged  mountains,  and  by 
that  fact  we  are  told  that  they  are  in  the  vigor  of  youth  or 
middle  life.  South  America  has  less  of  plateau  and  more 
of  low  plain  than  the  other  great  continents. 

175.  Earthquakes  in  mountain-making. — More  will  be 
said  about  earthquakes  in  the  chapter  on  volcanoes.     Any 


188    AN  INTRODUCTION  TO   PHYSICAL   GEOGRAPHY 


shock  given  to  the  firm  rocks  of  the  earth's  crust  causes 
vibration,  and  produces  a  shaking  of  objects  at  the  earth's 
surface.  In  straining  the  crust  enough  to  bend  thick  beds 
of  rock  many  sudden  breaks  and  slips  take  place,  which 
send  pulses,  or  shocks,  for  long  distances  through  the  rocks. 
Many  earthquakes  are  due  to  this  cause. 

176.  Mineral  products  of  mountain  regions.— As  we  have 
seen,  coal  is  found  among  the  mountains  of  Pennsylvania. 

So  is  it  in  Colorado,  as 
at  New  Castle.  But 
both  east  and  west,  coal 
is  also  found  where  the 
rocks  are  undisturbed. 
Coal  is  not  therefore 
a  result  of  mountain- 
building,  though  soft 
coal  may  be  changed  to 
anthracite  by  the  crush- 
ing that  goes  with  the 
rearing  of  mountains. 

But  many  of  the 
metals  are  found  chief- 
ly in  mountain  lands. 
It  is  there  that  they 
have  been  dissolved  out 
of  the  rocks,  often  by 
heated  waters,  and  de- 
posited in  mineral  veins 
(page  97).  Hence  it  is 
that  in  the  Cripple 
Creek  region  of  Colo- 
rado are  rich  gold- 
mines, and  in  the  Lead- 
ville  and  San  Juan  re- 
gions valuable  deposits  of  silver  and  lead.  The  metallic 
wealth  of  Wyoming,  Idaho,  Montana,  California,  Oregon, 


Fig.  135.— Placer  mining  in  North  Carolina. 
The  gold  is  separated  from  the  contained 
earth  by  means  of  a  swift  current  of  water. 


MOUNTAINS  AND  PLATEAUS  189 

and  Washington,  and  other  Western  States,  is  all  in  their 
mountain  lands.  In  connection  with  the  folding  and  crush- 
ing, the  various  ores  have  been  formed  by  the  slow  deposi- 
tion of  dissolved  matter  in  the  crevices  of  the  rocks.  The 
iron  and  copper  of  Lake  Superior  are  found  in  a  region 
of  ancient  mountains  now  worn  away. 

When  gold-bearing  veins  waste  away,  along  with  the 
general  wasting  of  a  mountainside,  the  gold  is  washed 
down  stream,  and  comes  to  rest  along  with  gravel  and  sand 
wherever  the  progress  of  the  waste  is  checked.  Such  gold- 
bearing  gravels  are  known  as  placer  beds,  and  the  washing 
of  the  gravels  to  separate  the  gold  is  known  as  placer 
mining  (see  Fig.  135). 

Not  all  mountains  contain  mineral  wealth.  Little  gold 
and  no  silver  is  mined  in  the  Appalachians.  The  Green 
Mountain  group  has  no  metals  of  importance,  but  is  rich 
in  slate  and  marble.  The  low  mountains  of  Saxony  have 
long  been  a  mining  center,  while  the  lofty  Alps  are  poor  in 
valuable  minerals. 

177.  Climate  of  mountains. — In  ascending  lofty  moun- 
tains one  finds  the  same  changes  of  climate  in  a  few  hours 
or  days  that  would  be  met  in  a  journey  from  tropical  or 
temperate  to  arctic  latitudes.  This  will  be  well  understood 
by  reviewing  the  belts  of  temperature  and  vegetation  in  the 
Alps.  On  the  plains  of  northern  Italy  the  olive  flourishes, 
and  in  the  deep  valleys  and  along  the  lower  slopes  the  vine 
abounds.  As  we  ascend  we  find  first  the  broad-leaved  for- 
est trees  to  heights  of  5,000  to  5,500  feet  on  the  south 
slope,  and  4,000  feet  on  the  north  slopes.  This  brings  out 
the  fact  that  climate  may  differ  much  on  two  sides  of  a 
mountain  range.  The  direct  rays  of  the  sun  and  the  winds 
from  the  warm  Mediterranean  affect  the  south  front  of  the 
Alps.  Above  the  deciduous  trees  come  the  cone-bearing 
or  evergreen  forests.  The  coniferous  trees  are  important 
in  preventing  floods  and  checking  avalanches,  as  well  as 
affording  supplies  of  timber  and  fire-wood  for  the  thrifty 


190    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


peasants.  Above  the  trees  are  the  upper  pastures,  brilliant 
with  flowers  of  every  hue,  to  which  the  flocks  and  herds 
are  driven  only  in  the  summer.  Still  above  is  the  zone  of 
rock  and  perpetual  snows.     Snows  may  wrap  the  highest 

summits, as  Mont  Blanc; 
while  often  the  upper 
mountains  are  so  steep 
for  thousands  of  feet 
that  the  snows  slide  off 
and  bare  crags  prevail. 
From  base  to  summit  of 
the  Alps,  one-fourth  is 
tillable,  one-half  is  for- 
est and  pasture,  and  the 
remaining  fourth  is  ut- 
terly barren. 

The  climate  of  north- 
ern Italy  is  warm- tem- 
perate, and  we  thus 
range  from  this  to  polar 
climate  as  we  ascend. 
If  we  rise,  however,  from 
the  foot  to  the  summit 
of  the  equatorial  Andes, 
we  there  range  from  a 
tropical  to  a  polar  cli- 
mate. In  the  far  north 
and  south  there  is  less 
contrast,  because  ice  and  snow  there  prevail  down  to  the 
level  of  the  sea,  as  upon  the  slopes  of  Mount  St.  Elias.  In 
the  United  States  the  Sierra  and  Cascade  Mountains  most 
nearly  represent  the  conditions  of  the'  Alps;  but  the 
Wasatch,  the  Eockies,  and  all  other  high  mountains  are 
belted  by  zones  of  climate — cooler  and  moister  above,  and 
warmer  and  drier  below. 

In  the  Appalachians  the  range  of  temperature  is  small, 


Pig.  136.— Vegetation  at  an  altitude  of  7,500  feet 
in  the  Rocky  Mountains  of  Montana ;  a 
patch  of  prairie  in  a  forest  of  fir. 


MOUNTAINS  AND  PLATEAUS  191 

because  the  mountains  are  low.  Still,  in  the  Adirondacks 
the  summits  are  always  cold  at  night,  the  mean  temperature 
for  the  day  is  never  high,  and  the  winters  are  long  and 
marked  by  heavy  snows.  Even  in  the  low  Berkshires  of 
Massachusetts  the  climate  is  much  cooler  than  in  the  adja- 
cent Hudson  and  Connecticut  valleys.  The  southern  Ap- 
palachians carry  a  wedge  of  cooler  climate  far  down  between 
the  hot  Carolina  coasts  on  the  east  and  the  half-tropical 
country  along  the  lower  Mississippi. 

178.  Life  of  mountain  lands. — Some  facts  belonging  to 
this  subject  have  already  been  given.  Thus  we  have  seen 
how  rapid  is  the  change  to  colder  climate  and  the  corre- 
sponding plants  as  we  rise  toward  the  tops  of  high  moun- 
tains ;  tillage  of  the  soil  is  confined  to  the  valleys  and 
lower  slopes,  while  grazing  and  timber  industries  run  to  the 
middle  slopes  or  to  the  summits,  according  as  the  mountains 
are  in  higher  or  lower  latitudes,  or  are  themselves  of  great 
or  small  altitude. 

In  the  mountainous  parts  of  Switzerland  the  peasants 
till  the  narrow  valley  bottoms,  reclaim  the  rough  surfaces 
of  the  torrent  fans,  and  raise  patches  of  grain  and  hay  on 
the  talus  and  other  waste  slopes.  The  dairy  is  a  chief 
means  of  support,  and  men,  women,  and  children  join  in  all 
the  industries  of  the  field,  while  wood-carving  and  other 
small  manufacturing  occupy  the  winter  months.  Houses 
are  built  of  wood,  with  wide-spreading  cornices,  the  thatch 
sometimes  weighted  down  with  large  stones.  The  splendid 
scenery  of  the  Alps,  close  to  many  populous  lands,  has 
made  Switzerland  the  "playground  of  Europe,"  and  the 
entertainment  of  tourists  may  be  called  the  chief  industry 
of  the  mountain  people. 

In  the  Eocky  Mountains  the  conditions  of  human  life 
are  entirely  different.  The  chief  attraction  in  these  moun- 
tains is  the  mining  of  the  precious  metals.  Instead  of 
humble  peasants,  native  to  the  soil  for  centuries,  we  find 
the  most  hardy  and  energetic  types  of  American  life  in  the 
14 


192    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

absorbing  search  for  mineral  wealth.  Mining  camps  which 
are  in  truth  cities,  spring  into  being,  and  as  swiftly  decay 
when  the  mines  cease  to  be  productive.  Agriculture  is 
possible  only  in  the  lowest  of  the  mountain  valleys,  and  is 
carried  on  mainly  in  the  adjacent  plains.  The  roadways 
have  been  built  not.  often  for  the  tourist,  but  almost  with- 
out exception  for  the  shipping  of  mineral  products  and  the 
introduction  of  supplies.  The  keen,  vigorous,  and  often 
rough  life  of  our  western  mountains  is  in  strong  contrast 
to  the  quiet  and  simplicity  of  Alpine  regions.  The  causes 
are  partly  geographic  and  partly  historical. 

As  New  York  and  other  cities  have  grown,  the  Adiron- 
dacks  have  become  chiefly  a  playground.  Lumbering,  al- 
ready far  too  destructive,  has  been  somewhat  restrained, 
and  the  summer  camp,  the  gun,  and  the  canoe  are  the  true 
symbols  of  the  region.  The  same  is  true  of  the  uplands 
of  New  England,  where,  indeed,  the  valleys  abound  in  farms 
and  villages,  but  the  mountains,  too  low  for  snow-field  and 
glacier,  are  forever  set  apart  to  rocky  ledge  and  forest. 

Ancient  and  worn  mountains  make  up  much  of  the 
rugged  surface  of  Wales.  No  precious  metals  occur,  but 
the  slate,  found  only  in  mountainous  countries,  furnishes, 
in  its  quarrying  and  shipping,  an  important  industry,  while 
in  the  south  are  deposits  of  coal,  leading  to  mining  and 
manufacture.  Similar  are  the  low  mountains  of  the  Eng- 
lish Lake  District.  Here,  howeyer,  there  are  no  impor- 
tant minerals,  but  lakes,  mountains,  and  beautiful  valleys, 
made  memorable  as  the  homes  of  Wordsworth  and  other 
men  of  letters,  the  whole  region  being  chiefly  a  summer 
refuge  for  toilers  from  the  cities. 

The  Scottish  Highlands,  with  their  thin,  cold  soils  and 
stretches  of  bare  rock,  their  rough  stone  cabins  and  un- 
changing poverty,  under  the  leaden  skies  of  the  north,  show 
us  still  another  type  of  the  life  of  mountain  lands.  No  great 
cities — diligent  but  small  tillage  of  the  soil,  isolation  and 
primitive  ways — such  is  the  life  of  mountains,  save  where 


MOUNTAINS  AND  PLATEAUS  193 

the  rocks  yield  coveted  treasure.  There  modern  life  pours 
in  like  a  tide,  and  the  virtues  and  vices  of  the  latest  civili- 
zation are  seen  to  the  full. 

179.  Barriers  and  passes. — Because  most  mountains  are 
in  the  form  of  long  belts  of  folding  and  uplift,  they  serve 
to  separate  the  lands  on  their  opposite  sides.  Thus  on 
the  east  of  the  Appalachians  are  the  low  plains  of  the 
Atlantic,  while  to  the  west  are  the  plateaus  that  extend 
from  north  to  south.  The  Mohawk  Valley  is  a  famous  gap 
in  this  great  system,  offering  a  gateway  from  the  Atlantic 
seaboard  to  the  interior.  More  will  be  said  about  the  Ap- 
palachian barrier  in  Chapter  XVI.  The  Eocky  Mountains 
form  a  strong  and  continuous  wall  between  the  Great  Plains 
and  the  Colorado  Basin.  It  is  partially  cut  by  the  deep 
gorge  of  the  Arkansas  Eiver,  but  beyond  that  one  must 
surmount  the  Marshall  Pass,  over  10,000  feet  in  altitude, 
or  other  and  higher  passes,  in  order  to  reach  the  Pacific 
slope.  In  Wyoming,  however,  the  Union  Pacific  Eailway 
finds  a  low  passage  at  about  8,000  feet.  On  the  west  of 
the  Sierra  Nevada  is  the  rich  and  fertile  valley  of  central 
California,  while  on  the  east  are  the  arid  slopes  and  salty 
basins  of  Nevada. 

The  Andes  show  marked  contrasts  on  east  and  west. 
The  Pacific  slope  is  relatively  dry,  while  the  Atlantic  moist- 
ure spreads  far  over  the  Amazon  plains  and  enriches  the 
head-waters  of  this  master  river  on  the  east  slopes  of  the 
mountains. 

In  the  Old  World  the  Pyrenees  are  an  effective  wall  be- 
tween France  and  Spain.  But  two  railways  join  the  coun- 
tries ;  one  of  these  follows  the  shore  of  the  Bay  of  Biscay, 
and  the  other  is  close  to  the  Mediterranean.  Carriage 
roads  cross  the  range  at  but  two  points.  The  Alps  are 
higher  and  more  rugged  than  the  Pyrenees,  and  through- 
out historic  time  have  stood  as  a  barrier  between  the  Med- 
iterranean and  central  Europe.  On  the  south  is  the  sub- 
tropical and  sunny  Italy.     On  the  north  are  the  cool  tern- 


MOUNTAINS  AND   PLATEAUS  195 

peratures  and  somber  skies  of  Germany.  But  the  passes, 
as  compared  with  the  Pyrenees,  are  low  and  numerous,  and 
have  been  trodden  by  travelers,  merchants,  and  invading 
armies  since  Eoman  days.  Trails,  beautiful  carriage  roads, 
and  railways  have  in  turn  assumed  the  chief  importance. 

In  Asia,  the  mild,  fertile,  and  crowded  districts  of  India 
are  shut  off  from  the  high,  cold,  wild,  and  sparsely  peopled 
lands  of  Tibet  by  the  Himalaya  Mountains,  while  the 
several  mountain  ranges  of  central  Asia  lie  between  the 
advancing  Eussians  on  the  north,  and  the  English,  en- 
trenched in  India,  on  the  south. 


CHAPTER  IX 

VOLCANOES 

We  shall  begin  our  study  by  looking  at  several  well- 
known  volcanic  regions,  the  one  about  the  Bay  of  Naples, 
the  Hawaiian  Islands,  and  Mount  Shasta.  We  shall  then 
compare  these  volcanoes,  and  see  what  great  principles  we 
can  find  to  help  us  understand  this  part  of  the  earth's  ma- 
chinery, which  is  so  strange  to  most  dwellers  in  the  United 
States.  The  first  examples  are  chosen  outside  our  North 
American  domain,  because  here  the  volcanoes  have  nearly 
ceased  to  be  active.  But  it  is  well  to  mention  at  the  outset 
that  nowhere  in  the  world  have  the  fires  of  the  earth  had 
more  effect  on  the  surface,  in  past  ages,  than  in  some  parts 
of  our  own  land. 

180.  Figurative  terms. — The  word  "  fire  "  in  the  last  sen- 
tence, and  in  other  passages  of  this  chapter,  is  not  used  in 
its  ordinary  sense,  but  somewhat  figuratively.  When  fire 
burns,  two  substances  combine — for  example,  coal  and 
oxygen— and  heat  and  light  are  caused.  The  substances 
are  said  to  be  consumed.  In  the  volcano  nothing  is  con- 
sumed ;  the  lava  as  it  comes  from  below  is  already  in  a  hot 
and  glowing  condition.  Before  the  real  facts  were  known, 
people  believed  the  heat  was  caused  by  burning,  and  the 
words  expressing  this  belief  are  still  used  in  speaking  of 
volcanoes.  Among  these  misleading  terms  are  flame,  ash, 
cinders,  and  igneous  (fiery)  rocks. 

181.  Vesuvius. — If  one  were  to  visit  the  west  coast  of 
Italy  and  ascend  this  mountain,  he  would  find  an  observa- 
tory part  way  up  the  slope,  where  for  many  years  Italian 

196 


VOLCANOES 


197 


scholars  have  watched  the  behavior  of  the  volcano.  This 
small  mountain,  about  4,000  feet  high,  rising  from  the 
shore  of  the  Bay  of  Naples,  is  a  good  sample  volcano ;  the 
better  because  it  has  been  studied  so  long,  and  its  principal 
changes  for  nearly  2,000  years  have  been  recorded.  That 
small  things  may  unfold  principles  is  as  true  in  geography 
as  in  all  other  fields  of  knowledge. 


Fig.  138.— Map  of  Mount  Vesuvius  and  vicinity. 

The  student  should  give  careful  attention  to  the  map 
(Fig.  138).  On  the  north  of  the  bay  are  a  number  of  lo- 
calities well  known  in  classic  story — Misenum,  Lake  Aver- 
no,  the  Elysian  Fields,  and  Puteoli  (Pozzuoli),  the  port  at 
which  Saint  Paul  landed  on  his  voyage  to  Eome.  Near  the 
shore  west  of  Naples  is  Monte  Nuovo,  or  new  mountain,  a 
hill  440  feet  high,  cast  up  by  volcanic  action  during  a  few 
days  in  September,  1538.  All  about  it  are  volcanic  hills  of 
earlier  origin,  and  two  islands  bordering  the  bay  are  also 
volcanic.     Thus  we  learn  that  Vesuvius  is  not  alone,  but  is 


198    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

surrounded  by  a  district  under  which  the  volcanic  heat  has 
been  more  or  less  active.  The  whole  region  is  subject  to 
earthquakes,  due,  it  is  believed,  to  the  pent-up  fires  below, 
and  when  the  volcano  gives  vent  to  the  confined  lava  the 
earthquakes  subside. 

Let  us  now  look  at  the  mountain  itself.  Sunk  into  its 
top  is  a  bowl- shaped  depression,  the  crater.  In  it  is  mol- 
ten rock,  and  from  it  there  come  forth  steam  and  other 
hot  vapors.  When  the  wind  is  right,  the  edge  of  the  crater 
can  be  reached  and  a  look  had  into  its  fiery  depths.  When 
a  powerful  eruption  begins,  immense  clouds  of  steam  rise 
and  spread  above  the  top  of  the  mountain,  taking  a  form 
that  has  often  been  likened  to  a  pine-tree.  It  is  not  smoke, 
but  vapor, that  pours  out ;  and  the  glow  often  seen,  especially 
at  night,  is  not  flame,  but  the  reflection  from  the  vapor 
clouds  of  the  light  that  flashes  up  from  the  melted  rocks, 
either  in  the  crater  or  overflowing  in  streams  that  roll  down 
the  sides  of  the  mountain. 

These  streams  sometimes  flow  so  fast  as  to  overtake  a 
man  running  swiftly.  At  other  times  they  creep.  The 
differences  depend  on  the  slope  and  on  the  consistency  of 
the  lava.  Some  lavas  are  thick  and  viscous,  like  molasses, 
others  are  thin  and  watery.  If  the  stream  is  shallow,  it  cools 
quickly  and  comes  to  rest.  After  lava  has  flowed  for  some 
distance  the  surface  cools  and  is  brittle,  while  the  lower 
parts  are  soft  and  hot.  As  these  lower  parts  push  on  they 
break  up  the  surface  into  a  rough,  clinkery  mass,  which 
appears  like  a  creeping  heap  of  slaggy  boulders.  After  the 
lapse  of  a  human  lifetime  a  lava  stream  may  still  send  steam 
forth  from  its  crevices,  while  the  surface  has  long  been 
cold,  hard  rock.  Lavas  are  often  frothy,  with  hot  vapor  in 
the  form  of  bubbles,  and  after  cooling  to  rock  are  full  of 
rounded  pores  or  cells.  Certain  lava-rocks  are  so  porous 
and  filmy  that  they  will  float  on  the  sea.  The  pumice-stone 
used  in  the  arts  is  a  volcanic  rock. 

As  the  lava  streams  of  Vesuvius  have  poured  down  its 


200    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

sides  they  have  added  successive  coats  to  its  slopes,  thus  in- 
creasing the  size  of  the  mountain.  But  not  all  the  growth 
of  the  cone  is  thus  explained.  Some  eruptions  take  place 
by  means  of  powerful  explosions,  whose  seat  is  somewhere 
below  the  outside  opening.  In  this  case  the  interior  rock 
comes  out,  not  as  lava,  but  in  the  form  of  fine  dust,  or 
coarser  pieces  of  rock,  which  fill  the  air,  and  fall  or  slowly 
sink  to  rest  on  the  sides  of  the  mountain  or  on  neighboring 
plains  and  seas.  Built  up  in  these  two  ways,  the  mountain 
mass  is  a  mixture  of  lava  torrents  and  "  ash  "  beds. 

The  student  will  observe  that  the  height  of  Vesuvius 
was  given  as  about  4,000  feet.  It  is  not  always  the  same, 
and  has  varied  several  hundred  feet  during  the  Christian 
era.  In  early  Eoman  times  the  volcano  had  always  been 
quiet,  though  previous  to  79  a.  d.  the  neighborhood  was 
shaken  by  earthquakes.  In  this  year  there  was  a  great 
eruption.  It  is  vividly  described  in  two  letters  written  by 
the  younger  Pliny  to  Tacitus  the  Eoman  historian.  These 
letters  referred  to  the  uncle  of  the  writer,  Pliny  the  Elder, 
the  great  naturalist,  who  at  that  time  commanded  a  fleet 
and  was  stationed  at  Misenum.  He  crossed  the  bay  to  see 
the  eruption  more  closely  and  also  to  rescue  a  friend,  and 
was  suffocated  in  the  fumes  of  the  volcano.  There  was  no 
lava,  but  immense  quantities  of  ash  were  thrown  out  and 
rained  on  the  neighboring  land  and  sea.  Two  cities,  Her- 
culaneum  at  the  west  foot,  and  Pompeii  at  the  south  base 
of  the  mountain,  were  buried  and  lost  for  many  centuries. 
Had  they  been  deluged  with  lava,  they  could  not  now  be  un- 
covered and  seen  in  such  perfection — walls,  pavements  worn 
by  wheels  of  carriages,  rooms,  wall-paintings,  utensils,  and 
all  the  signs  of  the  luxury  of  the  inhabitants.  As  the  cen- 
turies have  passed,  other  outbursts  have  sent  forth  streams 
of  lava  as  well  as  clouds  of  ash.  Sometimes  the  top  of  the 
cone  has  been  cut  off  several  hundred  feet  by  a  great  explo- 
sion, only  to  be  slowly  built  up  again  by  the  contributions 
of  more  quiet  eruptions. 


VOLCANOES  201 

182.  Other  Mediterranean  volcanoes. — With  what  we  have 
learned  about  Vesuvius,  it  will  now  be  useful  to  associate 
some  facts  about  other  volcanoes  in  the  middle  Mediterra- 
nean region.  South  of  Naples,  near  the  Straits  of  Messina, 
are  the  Lipari  Islands.  They  are  composed  of  volcanic 
rocks.  Of  several  volcanoes  in  this  group,  Stromboli  is 
best  known,  because  it  is  always  active.  Like  Vesuvius,  it  is 
sometimes  explosive  and  sometimes  quiet,  giving  forth  both 
molten  and  broken  material.  Its  perpetual  column  of 
steam,  illuminated  at  night  with  unfailing  regularity  by 
the  fires  of  the  crater,  has  caused  it  to  be  known  as  the 
"  Lighthouse  of  the  Mediterranean." 

Still  southward,  close  by  the  eastern  shore  of  Sicily, 
rises  another  volcano,  also  famed  in  classic  myth,  and  in 
comparison  to  which  Vesuvius  is  but  a  mound.  Etna  is 
more  than  10,000  feet  in  height,  and  has  a  circumference 
of  40  miles.  Like  Vesuvius,  this  vast  cone  is  built  chiefly 
of  lavas  and  ash  coming  to  rest  about  a  central  pipe  or 
throat  leading  up  from  the  depths,  but  there  have  also 
been  many  small  eruptions  on  the  flanks.  From  time  to 
time  cracks  open  on  the  sides  of  the  great  cone,  allowing 
the  escape  of  lava  and  cinders  and  causing  small  cones  to  be 
built.  Fig.  140  shows  some  of  these  minor  cones  in  process 
of  formation.  Like  other  great  mountains,  it  has  a  rug- 
ged surface,  and  rises  through  several  zones  of  climate, 
being  almost  tropical  at  its  base,  temperate  and  forested 
on  its  middle  slopes,  and  arctic  and  snowy  toward  its 
summit.  One  German  scholar  has  written  two  great 
volumes,  wholly  given  to  a  description  and  history  of  this 
single  volcano. 

In  1831  the  sea  south  of  Sicily  gave  a  fine  illustration  of 
the  volcanic  habit  of  that  region.  At  a  point  where  the 
water  was  600  feet  deep,  volcanic  materials  were  cast  up 
until  they  stood  200  feet  above  the  water.  This  new  island, 
however,  was  soon  cut  away  by  the  sea  waves,  leaving  a 
shoal  where  the  transient  land  had  been. 


VOLCANOES  203 

183.  Hawaiian  volcanoes. — The  Hawaiian  Islands  form  a 
northwest  by  southeast  chain,  about  400  miles  long.  All 
are  volcanic  piles  built  up  from  the  floor  of  the  deep  seas. 
The  onl}^  active  volcanoes,  however,  are  on  Hawaii,  the 
southeastern  member  of  the  series.  This  is  a  large  island, 
about  80  miles  across  and  having  the  form  of  a  rude  tri- 
angle. The  two  highest  volcanoes  are  Mauna  Loa  and 
Mauna  Kea,  rising  nearly  14,000  feet  above  the  sea.  The 
total  height  above  the  sea  bottom  is  about  30,000  feet,  or 
in  the  neighborhood  of  6  miles.  If  the  sea  could  be  drained 
away,  this  whole  island  would  be  a  broad-topped  mountain, 
as  high  as  the  loftiest  summits  of  the  Himalayas.  Succes- 
sive outpourings  of  lava  have  reared  the  islands  from  the 
floor  of  the  sea.  The  work  of  Vesuvius  or  even  of  Etna  is 
insignificant  as  compared  with  this. 

The  slopes  of  the  Hawaiian  cones  are  very  gentle  (Fig. 
142).  This  is  due  to  the  fact  that  the  rocky  matter  sent 
forth  is  all  in  the  form  of  lava,  and  the  lava  is  in  a  very 
liquid  condition.  Hence  when  it  flows  out,  it  spreads  widely. 
Thicker  lavas  and  falling  ash  build  steeper  cones.  There 
is  great  difference  between  the  craters  of  Vesuvius  and 
Hawaii.  The  one  is  a  narrow,  steep-sided  bowl,  the  others 
are  broad,  sunken  basins  several  miles  across  (Fig.  141). 
The  walls  of  Hawaiian  craters  are  cliffs  several  hundred 
feet  high,  but  at  some  points  descent  can  be  made.  During 
the  time  of  quiet  between  eruptions,  the  traveler  finds  a 
floor  of  cooled  lava  covering  over  most  of  the  crater  basin. 
But  at  some  points  there  are  small  ponds  or  lakes  of  mol- 
ten lava,  which  bubbles  and  sputters  with  the  escape  of  hot 
vapor. 

The  eruptions  are  vaster  but  more  quiet  than  those 
of  many  small  volcanoes.  For  a  number  of  years  the  lava 
may  rise,  and  spread  in  the  crater,  so  that  the  basin  can  no 
longer  be  entered.  But  it  has  not  been  known  to  flow  over 
the  rim.  Before  this  is  reached  it  pushes  through  deep- 
seated  cracks  and  issues  on  the  sides  of  the  mountain,  often 


m 


M 


h 


204 


VOLCANOES 


205 


several  miles  away  from  the  crater,  and  flows  down  the 
slope  as  a  great  hot  river.  Being  very  liquid  at  the  start, 
it  flows  long  distances,  sometimes  as  far  as  50  miles.  Some- 
times it  has  reached  the  seashore,  and  there,  like  a  >vater- 
fall,  has  poured  over  the  sea  cliffs  upon  the  beach  below. 

Much  of  the  surface  of  the  islands  is  mantled  with  soil 
and  forest.  But  where  the  outflows  have  been  recent,  as 
over  a  large  part  of  Hawaii,  the  lava  surfaces  are  rugged 
and  utterly  barren.  In  the  forested  regions  streams  are 
abundant,  and  some  of  them  have  worn  out  deep  gorges 


r-'^4^.^s:%^^4^^^ 


Fig.  143.— a  cuugualcd  lava  cascade ;  Hawaii. 

which  add  variety  to  the  surface.  Thus  volcanic  action, 
weathering,  and  stream  erosion  combine  to  give  the  land  its 
form  and  expression,  and  the  climate,  moist  and  tropical, 
clothes  much  of  the  surface  with  ferns,  breadfruit-trees, 
screw-pines,  and  coconut  palms. 

184.  Krakatoa. — Like  the  Hawaiian  group,  many  islands 
of  the  Paciflc  Ocean  are  volcanic.  They  are  the  "  high  " 
islands,  in  distinction  from  those  that  are  low,  or  of  coral 
origin.     Krakatoa  is  an  island  volcano,  lying  in  the  strait 


206    AN  INTHODUCTIOH  TO  PHYSICAL  GEOGRAPHY 

that  separates  Sumatra  and  Java.  It  was  not  known  as  a 
great  volcano  until  August,  1883,  when  for  two  days  a  suc- 
cession of  explosions  blew  away  about  half  of  the  island 
mountain,  brought  the  neighboring  seas  and  lands  to  total 
darkness,  impeded  the  sailing  of  ships  by  the  ash  that  fell 
on  the  sea,  and  gave  forth  reports  which  were  heard  in 
Bangkok,  in  the  Philippine  Islands,  in  Australia,  and  more 
than  2,000  miles  to  westward  in  the  Indian  Ocean.  Dust 
fell  on  ships  1,600  miles  away,  and  is  believed  to  have  been 
carried  in  the  upper  air  around  the  world  (Sec.  205).  The 
student  will  find  it  profitable  to  consider  the  strong  con- 
trasts between  this  and  the  Hawaiian  Group. 

185.  Mount  Shasta. — This  volcano  is  no  longer  active,  but 
is  none  the  less  useful  for  comparison  with  those  already 


Fig.  144.— Mount  Shasta. 


studied.  It  is  in  northern  California  and  rises  to  an  alti- 
tude of  11,000  feet  above  neighboring  lowlands.  Its  slopes 
are  steep  above,  and  become  gradually  gentler  below,  until 
they  merge  with  the  plain.     The  upper  part  of  the  moun- 


VOLCANOES  207 

tain  is  double,  its  two  summits  marking  two  principal 
points  of  eruption.  The  higher  is  also  the  older;  it  had 
been  completed  and  had  begun  to  waste  away  before  the 
building  of  the  other.  Fig.  144  shows  only  the  older*  sum- 
mit, the  younger  being  hidden  behind  it. 

If  one  were  to  dig  deep  into  the  mountain  mass  he  would 
find  various  beds,  some  of  ash,  bound  into  firm  rock,  and 
some  of  cool  lava,  thus  showing  that,  like  Vesuvius,  the  vol- 
cano was  sometimes  explosive  and  sometimes  sent  streams 
of  molten  rock  welling  forth  from  its  crater.  On  the  lower 
slopes  of  the  mountain  are  smaller  cones,  as  in  the  case  of 
Etna,  and  some  of  these  are  much  younger  than  either  of 
the  great  peaks.  From  one  of  them  a  lava  stream  flowed 
to  the  Sacramento  River  and  followed  its  valley  for  50 
miles.  The  river  has  since  opened  a  canyon  across  it,  and 
elsewhere  sunk  a  deep  channel  at  its  side  so  as  to  leave  the 
lava  plain  as  a  high  terrace. 

For  a  long  period,  as  we  reckon  time,  the  fires  below  the 
mountain  have  gone  out,  or  at  least  have  been  unable  to 
send  forth  the  signs  of  their  presence.  We  call  the  vol- 
cano extinct.  Instead  of  fire,  glaciers  cling  to  its  upper 
slopes.  There  are  five  of  them,  two  to  five  miles  in  length, 
each  scooping  a  glacial  alcove  and  trough  out  of  the  sides 
of  the  peak,  and  strewing  the  space  below  with  moraine,  or 
sending  rock-flour  and  pebbles  down  the  torrent  courses 
of  the  mountain.  The  torrents  have  dug  deep  gorges.  So 
the  forces  of  waste  are  striving  to  tear  down  what  the  vol- 
canic forces  have  built  up. 

186.  Other  volcanoes  of  the  western  United  States. — If  we 
go  northward  from  Mount  Shasta  along  the  Cascade  Range 
of  Oregon  and  Washington,  we  find  magnificent  volcanic 
peaks,  of  which  the  highest  is  Mount  Rainier,  rising  to  14,500 
feet  above  the  sea.  Standing  on  a  broad  plateau  and  apart 
from  other  high  summits,  it  is  an  imposing  landmark, 
seen  afar  from  the  cities  and  the  sea.  As  measured  by  the 
amount  of  wear,  it  is  older  than  Shasta.  Its  glaciers  and 
15 


208    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


Fig.  145.— Upper  part  of  Mount  Hood,  Orejjon, 
shrouded  by  snow  and  ice. 


torrents  have  deepened  and  enlarged  their  valleys  nntil  the 
intervening  ridges  are  narrow  and  crusted.  It  may  be  said 
also  to  have  renewed  its  youth,  for  after  the  work  of  de- 
struction had  made 
great  progress  its 
fires  broke  forth 
once  more  and 
constructed  a  well- 
formed  cone  and  cra- 
ter at  top.  Mount 
Hood,  Mount  Jef- 
ferson, Mount  St. 
Helens,  and  Mount 
Baker  are  among 
the  other  volcanoes 
of  the  region.  All 
of  these  lofty  peaks  are  white  above  and  forested  below. 
"  Could  an  observer  obtain  a  bird's-eye  view  of  the  Cas- 
cade Mountains,  they  would  appear  as  a  belt  of  emerald 
studded  at  irregular  intervals  with  immense  brilliants " 
(Russell). 

Mount  San  Francisco  in  northern  Arizona  and  Mount 
Taylor  in  northern  Xew  Mexico,  each  rising  5,000  feet  above 
the  plateau,  are  conspicuous  landmarks,  though  less  massive 
than  the  cones  of  the  Pacific  region.  They  are  old  and 
worn,  but  near  their  bases  are  ash-rimmed  craters  and  black 
jagged  lava  fields  so  young  that  soil  and  plants  have  not  yet 
begun  to  cover  them.  From  the  top  of  Mount  San  Francisco 
one  may  look  down  into  more  than  60  craters.  The  num- 
ber of  small  volcanoes  scattered  through  the  Cordilleras 
is  great,  and  a  few  are  found  along  the  western  border 
of  the  Great  Plains.  They  are  of  all  ages,  and  some  have 
doubtless  been  active  within  a  few  centuries ;  but  no  erup- 
tions have  been  witnessed  by  white  men. 

187.  Regions  of  active  volcanoes. — We  have  selected  cer- 
tain volcanoes  because  they  are  especially  instructive,  and 


VOLCANOES  209 

we  have  seen  some  of  the  principles  that  arise  from  their 
study.  Another  general  fact  is  that  they  are  confined  to 
no  part  of  the  world,  but  form  one  of  the  common  features 
of  the  earth's  surface. 

The  Atlantic  Ocean  contains  many  volcanic  islands. 
Iceland  is  one  of  the  most  northerly  and  important.  Its 
lava  streams  are  of  great  size,  while  the  ash  from  some  of 
its  volcanoes  has  fallen  on  ships  in  the  northern  seas,  has 
descended  on  Scandinavia,  and  has  even  injured  crops  in 
the  north  of  Scotland.  Farther  south,  the  Azores,  Canary, 
Cape  Verde,  St.  Helena,  and  other  islands  are  volcanic. 

In  the  West  Indies  is  a  line  or  narrow  belt  of  volcanoes 
500  miles  long.  They  make  the  higher  islands  of  the  Lesser 
Antilles,  including,  among  others,  St.  Kitts,  Guadeloupe, 
Martinique,  and  St.  Vincent.  Because  they  are  arranged 
in  a  line,  it  is  thought  that  they  are  related  to  one  another 
in  origin,  and  make  up  a  system.  Their  eruptions,  though 
not  frequent,  have  been  energetic  and  destructive.  Here, 
as  about  Vesuvius,  the  long  periods  of  rest  have  given  a 
false  sense  of  security,  and  tempted  to  extensive  settle- 
ment on  the  rich  volcanic  soils,  to  be  followed  by  fearful 
disaster  when  activity  was  resumed.  There  were  outbreaks 
on  St.  Vincent  in  1718  and  1812,  on  Guadeloupe  in  1797, 
and  on  Martinique  in  1851.  The  outbreak  of  1812  was  an 
explosion  almost  rivaling  that  of  Krakatoa.  A  crater  called 
Soufriere  was  either  created  or  greatly  enlarged,  the  fertile 
lands  of  the  island  were  overwhelmed  by  ashes,  and  the 
town  of  Caracas,  with  10,000  inhabitants,  suifered  the  fate 
of  Pompeii. 

In  May,  1902,  while  the  type  for  this  book  is  being  set, 
the  attention  and  sympathy  of  the  world  are  again  drawn 
to  these  unhappy  islands.  The  Soufriere,  after  a  rest  of 
ninety  years,  and  the  Pelee  volcano  on  Martinique,  which 
had  slumbered  for  fifty-one  years,  have  again  wakened  to 
activity.  Explosions  scatter  stones  and  ashes  widely  over 
the  lands.      Streams  of  hot  mud  are  flowing  from  the 


210     AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

crater  to  the  sea.     A  sudden  blast  of  steam  and  hot  cinders, 
sweeping  down  the  mountain  slope  with  hurric'ane  force, 


Fig.  146.— Interior  of  the  crater  of  Mount  Misery,  on  St.  Kitts,  West  Indies.    It  is 
still  steaming,  though  so  old  that  its  lavas  are  covered  by  soil  and  plants. 


has  destroyed  the  city  of  St.  Pierre.  More  than  30,000  in- 
habitants of  the  islands  have  lost  their  lives,  and  great 
areas  are  laid  waste. 

We  have  already  told  of  a  few  great  cones  of  the  Pacific 
coast  region.  Following  the  mountain  belt  through  Mex- 
ico and  Central  America  and  far  along  the  Andes,  great 
volcanoes  are  abundant  and  active.  Xorthward,  a  few  vol- 
canoes occur  on  the  islands  of  southern  Alaska,  and  a  great 
volcanic  belt,  beginning  on  the  south  coast  of  western 
Alaska,  may  be  followed  almost  around  the  Pacific  Ocean. 
The  Aleutian  Islands,  Kamchatka,  the  Kuril  Islands,  Japan, 


VOLCANOES 


211 


the  Philippine  Islands,  and  those  of  more  southern  seas, 
with  the  mountains  of  western  America,  almost  girt  this 
vast  ocean  with  fire,  while  many  a  chimney,  as  we  have 
seen,  rises  from  its  waters,  and  many  submarine  volcanoes 


Fig.  147.— a  volcanic  crater,  holding  a  lake ;  Costa  Rica. 


have  not  been  able  to  pile  their  outpourings  to  the  surface 
of  the  sea.  Krakatoa  belongs  to  a  field  of  great  volcanic 
activity,  including  Java,  Sumatra,  and  almost  all  parts  of 
the  East  Indies. 

188.  History  of  a  volcanic  cone. — This  is  a  story  of 
growth  and  decay.  Vesuvius,  Etna,  and  the  Hawaiian 
cones  are  still  growing.  The  time  was  when  their  piles  of 
volcanic  matter  were  small  like  Monte  Xuovo.  Through 
progressive  stages  they  have  grown  to  be  what  they  are. 
In  time  they  will  cease  to  send  forth  ash  and  lava,  and 
destruction  will  begin.  We  see  the  first  stages  of  it  in 
Mount  Shasta.     Here  the  form  is  still  well  preserved,  and 


212    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


the  mountain  has  lost  little  from  its  top  and  sides.  But 
there  has  been  some  wasting.  The  glaciers  are  scooping 
out  the  higher  slopes,  and  the  torrents  are  furrowing  the 
lower  with  ravines.  In  time  the  summits  will  yield,  the 
ravines  will  become  vast  canyons,  and  the  volcanic  pile  will 
be  deeply  cut  and  scarred.  This  stage  is  well  illustrated 
by  Tahiti,  a  high  volcanic  island  in  the  Pacific  Ocean.  A 
series  of  radiating  valleys,  like  the  spokes  of  a  wheel,  head 
abruptly  toward  the  center  and  summit,  and  extend  out  to 
the  shores  of  the  island.  These  valleys  are  sometimes 
3,000  feet  deep,  and  have  so  widened  that  a  ridge  like  the 
edge  of  a  knife  is  all  that  is  left  between  them.  Dana 
ascended  to  the  top  along  one  of  these  ridges,  whose  upper 
edge  was  in  places  but  1  to  3  feet  wide,  while  the  cliffs 
below  were  1,000  to  2,000  feet  high  and  stood  at  an  angle 
of  60°  to  70°. 

We  can  readily  see  that  in  time  these  sharp  ridges  will 
break  down,  the  gorges  be  extended  at  their  heads,  the 
summits  decay  and  thus  the  height  be  lessened,  the  rough 
surface  become  subdued,  and,  if  time  enough  be  granted, 
the  entire  island  will  be  worn  down  to  the  level  of  the  sea. 

The  student  should  imagine 
all  this,  and  the  picture  thus 
formed  will  be  true  to  nature. 
In  many  parts  of  the  world 
are  found  volcanic  mountains 
which  have  been  worn  away  un- 
til the  merest  stumps  and  roots 
remain.  This  is  best  under- 
stood by  reference  to  the  dia- 
gram (Fig.  148).  We  see  first 
the  original  profile  of  the  cone ; 
second,  we  have  a  low,  subdued 
pile  or  hill,  still  rising  above 
the  general  surface ;  third,  all  of  the  original  cone  is  gone, 
and  much  of  the  surface  rock  in  the  surrounding  region. 


Fig.  148.— Ideal  sections  of  a  wast- 
ing volcanic  cone  at  three  stages 
of  its  history. 


VOLCANOES 


213 


Fig.  149.— a  volcanic  neck ;  northern  New 
Mexico. 


But  the  lava  that  occupied  the  old  throat,  far  below  the 
crater,  is  harder  than  the  surrounding  rock,  and  in  the 
great  wasting,  has  sur- 
vived and  stands  above 
the  surface.  It  has 
been  well  likened  to 
the  cork  in  a  bottle, 
and  geologists  call  it 
a  volcanic  neck  or 
plug.  Many  of  them 
stand  out  on  the  sur- 
face of  the  plateau  in 
parts  of  New  Mexico 
(see  Fig.  149). 

189.  Sheets  of  lava. — While  no  lavas  are  so  fluid  as 
water,  they  show  great  differences  in  this  respect.  Some 
are  very  stiff  and  can  scarcely  flow  at  all ;  others  are  thin 
and  flow  easily.  When  a  lava  stream  starts  from  a  crater 
it  also  begins  to  cool  and  it  stops  flowing  when  it  gets  so 
cool  as  to  be  stiff.  If  the  amount  which  comes  out  is  small 
it  stops  quickly.  The  piling  up  of  such  short  streams 
makes  volcanic  mountains.  But  sometimes  a  very  large 
quantity  of  very  thin  lava  escapes  all  at  once,  and  then  it 
runs  farther  and  spreads  more  widely.  If  it  runs  into  a 
valley  or  over  a  plain  it  makes  a  lava  lake.  When  it 
hardens  it  makes  a  broad,  flat  sheet  of  lava-rock.  In  the 
basin  of  the  Columbia  Eiver  there  have  been  many  such 
eruptions,  with  the  result  that  broad  plains  are  composed 
wholly  of  volcanic  rocks,  piled  up  in  sheets.  The  Snake 
River,  crossing  such  a  plain,  has  made  a  long,  deep  canyon 
(Fig.  51),  in  the  walls  of  which  the  sheets  or  beds  of  lava- 
rock  are  arranged  like  the  beds  of  sandstone  and  limestone 
in  the  canyons  of  the  Colorado.  Before  the  eruptions  began, 
the  region  had  for  long  periods  been  a  district  of  mountains 
and  valleys.  Hence  the  outpourings  flooded  fhe  valleys  and 
low  grounds,  while  the  higher  mountains  still  rise  as  islands 


214    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

from  the  plateau,  or  send  out  ridges  or  spurs  from  its  bor- 
der. Thus  the  boundary  of  the  lava  sheets  runs  in  and  out, 
like  the  shore-line  of  a  lake  in  a  rough  country. 

There  have  been  volcanic  eruptions  in  all  the  past  ages 
of  the  earth.  Some  of  these  spread  under  the  ocean  and 
were  covered  by  sediments,  and  so  there  are  lava-rocks 
buried  among  the   stratified  rocks.     Lavas  have  also  in- 


truded themselves  in  broad  sheets  between  strata  and  there 
hardened  to  rock.  Afterward,  when  great  series  of  strata 
have  been  lifted  into  the  air  and  gradually  wasted  away, 
the  sheets  of  lava-rock  have  been  exposed  to  view;  and, 
being  very  durable,  they  often  stand  forth  in  the  landscape 
as  hills  and  ridges.  The  AVatchung  Mountains  of  Xew 
Jersey,  the  Palisades  of  the  Hudson  (Fig.  150),  and  Mount 
Holyoke  in  Massachusetts  are  of  this  character. 

The  cliffs  at  the  edges  of  the  sheets  have  a  peculiar 


216    AN   INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

character  because  of  a  tendency  of  lava-rock  to  break  up 
into  columns.  It  shrinks  and  cracks  in  cooling  just  as 
mud  cracks  in  drying,  and  the  cracks  run  far  into  it, 
dividing  it  into  long  blocks  with  five  or  six  sides  (Fig.  151). 


Fig.  153.— Bird's-eye  view  of  Crater  Lake,  Oregon. 

Extensive  sheets  of  lava  are  found  in  Colorado,  Utah, 
Arizona,  New  Mexico,  and  other  western  States.  Some- 
times they  have  been  worn  away  to  small  remnants,  as  in 
the  lava  caps  of  ISTorth  and  South  Table  Mountain  at 
Golden,  Colorado,  or  Castle  Eock,  south  of  Denver.  From 
the  latter  place  is  quarried  a  gray  or  pinkish  lava  which  is 
used  as  a  building  stone  in  that  region. 

In  western  Scotland  are  important  lava  sheets  also. 
Here  belong  the  columnar  rocks  of  Mull,  Staffa,  and  other 
islands,  which  consist  largely  of  remnant  lava-beds.  Into 
the  southern  cliffs  of  Staff  a  the  sea  has  worn  Fingal's  Cave 
by  removing  the  vertical  columns  of  lava.  Giant's  Cause- 
way, on  the  shore  of  Ireland,  consists  of  similar  volcanic  rock. 
One  of  the  largest  outpourings  in  the  world  forms  the  pla- 
teau known  as  the  Dekkan  in  India.  The  lavas  are  some- 
times 6,000  feet  thick. 


VOLCANOES 


217 


190.  Volcanic  lakes. — These  may  be  formed  in  at  least 
two  ways :  A  flood  of  lava  sometimes  blockades  a  valley ; 
behind  such  a  dam  a  lake  will  form  and  remain  until  the 
basin  is  full  of  sediment,  or  the  outlet  stream  saws«  through 


Fig.  153.— "Mount  Mazama, 


an  ideal  restoration  of  the  Crater  Lake  volcano. 
FiR.  152  and  Sec.  190. 


See 


the  barrier.  And  when  a  volcano  becomes  extinct  its  crater 
may  serve  as  a  water-basin  (Fig.  147).  Crater  Lake,  in 
southern  Oregon,  lies  in  the  heart  of  an  old  volcano,  the 
higher  and  central  parts  of  which  have  disappeared.  In- 
stead of  an  explosion,  as  in  the  case  of  Krakatoa,  there  was 
a  withdrawal  of  the  lava  beneath,  so  that  all  the  upper 
part  of  the  cone,  with  its  gorges  and  glaciers,  fell  in  and 
disappeared,  leaving  a  nearly  circular  pit  4,000  feet  deep 
and  6  miles  wide  (Fig.  152).  The  water  of  the  lake  is 
2,000  feet  deep.  Above  it  rises  an  island,  which  is  a  small 
volcanic  cone,  made  after  the  disappearance  of  the  greater 
cone. 

191.  Volcanic  soils. — Lavas  and  ash  are  often  so  porous 
that  they  are  easily  entered  by  air  and  water,  and  weather 
rapidly  into  soils.     Thus,  after  a  few  generations,  the  lava 


218    AN  INTRODUCTION  TO  PHYSICAL   GEOGRAPHY 

fields  about  Vesuvius,  and  other  volcanoes  in  genial  climates, 
become  densely  populated,  and  all  danger  from  eruptions 
seems  forgotten.  Parts  of  the  Dekkan  are  important  in 
wheat  and  cotton  growing,  and  the  black  and  fertile  soil  is 
due  to  the  decay  of  the  lavas.  In  the  same  way  lavas  fur- 
nish the  soils  for  extensive  wheat-fields  in  Oregon  and 
Washington.  Thig'  is  perhaps  the  most  important  way  in 
which  volcanoes  affect  mankind,  unless  we  except  the  catas- 
trophes which  have  wrought  destruction  of  life.  The  vol- 
cano does  not  compare  with  weathering  or  with  streams ; 
and  it  probably  has  not  influenced  the  more  progressive 
races  so  extensively  as  has  the  glacial  invasion.  Certainly 
glaciers,  much  more  than  volcanoes,  have  molded  the  condi- 
tions of  life  in  the  United  States. 

192.  Causes  of  volcanic  explosions. — The  general  causes 
of  volcanoes  are  not  well  known,  but  the  reason  that  lavas 
sometimes  explode  is  better  understood.  There  is  water  in 
all  lavas,  the  quantity  being  large  in  some  and  small  in 
others.  Deep  down  in  the  earth's  crust  the  pressure  is  so 
great  that  the  water,  though  intensely  hot,  can  not  change 
to  vapor ;  but  as  the  lavas  rise  they  experience  less  and  less 
pressure  until  at  last  the  water  within  them  suddenly  be- 
comes steam  and  is  instantaneously  expanded.  If  there  is 
little  water,  the  lava  quietly  bubbles  ;  if  there  is  much,  it 
is  torn  to  fragments,  and  the  fragments  are  hurled  into  the 
air.  The  principle  of  the  explosive  volcano  is  the  same  as 
the  principle  of  the  geyser. 

193.  Summary  of  principles. — The  descriptions  of  par- 
ticular volcanoes  and  districts  have  illustrated  various  gen- 
eral facts,  and  some  of  these  have  been  pointed  out.  We 
now  bring  together  the  more  important : 

(1)  Many  volcanoes  build  around  their  vents  a  cone ; 
it  may  be  of  mountainous  height,  and  the  term  moun- 
tain, in  a  general  sense,  is  commonly  used.  It  is  not  at  all 
due  to  uplift  of  the  earth's  crust,  but  to  the  bringing  up  of 
materials  from  below  which  are  heaped  up  about  an  open- 


VOLCANOEIS  210 

ing.     In  this  respect,  as  well  as  in  form,  the  volcano  finds 
its  miniature  representative  in  the  ant-hill  (Fig.  58). 

(2)  Some  cones  are  large  both  in  height  and  base,  like 
the  Hawaiian,  while  others  are  small,  like  Vesuvius,  Strom- 
boli,  or  the  diminutive  Monte  Nuovo.  They  also  differ  in 
form ;  some  are  very  flat  and  others  as  steep  as  a  talus  of 
coarse  waste,  the  difference  being  due  to  the  character  of 
the  materials  forming  the  pile. 

(3)  The  materials  sent  forth  are  various.  First,  we 
have  the  lavas,  and  these  differ  much.  Some  are  dark  and 
very  heavy,  as  basalt,  and  others  are  pale  in  color  and  lighter 
in  weight.  Second,  we  find  the  ash,  with  larger  angular 
pieces  of  rock,  as  in  some  eruptions  of  Vesuvius  and  Shasta, 
or  the  great  eruption  of  Krakatoa.  Of  importance  also  are 
the  vapors,  particularly  the  steam,  which  often  condenses 
and  causes  heavy  rains,  or  mixing  with  the  ash  gives  rise 
to  eruptions  of  mud,  which  flow  from  the  volcano  and 
harden  into  rock.  Any  volcanic  ash  which  thus  becomes 
bound  into  firm  rock  is  called  Volcanic  Tuff. 

(4)  Volcanoes  differ  much  in  the  manner  of  eruption. 
Stromboli  is  constant ;  Vesuvius  and  the  Hawaiian  volca- 
noes are  intermittent  or  spasmodic.  Some  are  quiet ;  others 
are  violent  and  explosive.  Some  vents  emit  many  small 
eruptions  and  build  up  mountains ;  others  discharge  great 
volumes  of  their  lava  and  construct  plains. 

(5)  Craters  are  formed  in  various  ways.  Fragments 
thrown  out  by  explosive  eruptions  fall  to  the  ground  all  about 
the  opening,  and  thus  build  up  a  circular  rim.  Sometimes  a 
great  explosion  blows  off  the  upper  part  of  a  conical  moun- 
tain, leaving  a  hollow  in  its  place.  And  sometimes  the  in- 
terior of  the  mountain  is  melted  out,  letting  the  top  fall  in. 

(6)  A  volcano,  like  a  mountain  range,  is  caused  by  forces 
belonging  to  the  mysterious  interior  of  the  earth.  As  soon 
as  made  it  is  attacked  by  the  destructive  forces  of  air  and 
water,  which  gradually  wear  it  away.  Growth  and  decay 
make  up  the  history  of  its  life. 


220    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

Eakthquakes. 

194.  In  volcanic  regions.— The  earthquake  and  the  vol- 
cano often  go  together.  Thus,  earthquakes  are  common 
about  Xaples  and  Mount  Vesuvius.  Before  the  great  erup- 
tion of  79  A.  D.,  shakings  of  the  earth  had  occurred  for  sev- 
eral years.  When  the  energy  that  had  been  sealed  below 
the  surface  broke  forth,  the  shaking  ceased.  Still  farther 
south  in  Italy  great  earthquakes  have  shaken  the  Calabrian 
region  repeatedly.  For  four  years,  beginning  in  1783,  they 
were  almost  constant.  Nine  hundred  and  forty-nine  shocks 
took  place  in  the  single  year  1783.  Over  a  large  district 
all  the  villages  and  towns  were  reduced  to  ruins.  The  sur- 
face often  rolled  like  sea  waves ;  trees  rocked,  and  monu- 
ments were  thrown  down,  or  twisted  about  on  their  founda- 
tions. Deep  fissures  and  ravines  were  opened  in  the  soil 
and  in  the  rocks.  Animals,  and  even  houses,  were  engulfed 
in  some  of  these.  In  some  places  funnel-shaped  basins  were 
formed  and  occupied  by  water,  thus  creating  ponds  or  small 
lakes.  In  the  mountain  regions,  landslides  occurred,  and 
rivers  were  in  some  cases  turned  from  their  course.  In 
certain  places  whole  villages  were  swept  away  in  these 
slips.  On  the  shore,  the  inrushing  of  great  waves  destroyed 
much  life  and  many  homes.  Such  waves  are  due  to  the 
shaking  of  the  earth's  crust  and  should  never  be  called 
tidal.  About  40,000  people  lost  their  lives  directly  through 
these  earthquakes,  while  many  others  died  of  pestilence  or 
neglect. 

The  Calabrian  shocks  must  serve  as  an  illustration  of 
many.  New  Zealand,  Chile,  the  East  Indies,  and  Japan 
have  all  suffered  from  powerful  disturbances.  Nowhere ' 
has  there  been  greater  havoc  than  in  closely  peopled 
Japan.  Deep  fissures,  houses  and  towns  shaken  down,  and 
enormous  waves  rolling  in  from  the  Pacific  and  destroying 
thousands  of  lives — such  are  the  features  of  Japanese  earth- 
quakes. 


VOLCANOES 


221 


195.  Charleston  earthquake.  —  The  date  of  this  great 
shock  is  1886.  It  took  place  at  9.50  p.  m.,  August  31,  and 
lasted  for  a  little  more  than  a  minute.  Every  building  in 
Charleston  was  more  or  less  injured,  thousands  of  chimneys 
were  thrown  down,  and  the  ground  rocked  so  as  to  give 
the  impression  of  a  heavy  sea.  Near  the  city,  the  railway 
tracks  were  severely  twisted  in  a  number  of  places,  cracks 


Fig.  154.— street  scene  in  Charleston  after  the  earthquake. 

opened  in  the  ground,  and  water  was  cast  up.  The  shock 
was  felt  in  the  Northern  as  well  as  the  Southern  States, 
and  even  in  the  Province  of  Ontario.  At  least  2,500,000 
square  miles  were  aifected  by  it.  By  comparison  of  times 
in  the  different  places,  it  was  found  that  the  earthquake 
wave  traveled  150  miles  per  minute.  This  shock  was  not 
connected  with  an  eruption,  and  Charleston  is  far  from  any 
active  volcanoes. 


222    AN  INTRODtTCTlON  TO  PHYSICAL  GUOGKAPHY 


196.  What  is  an  earthquake? — It  is  not  so  easy  to  answer 
as  to  ask  this  question.  It  is  quite  clear  that  the  rocks  of 
the  earth's  crust  receive  an  impulse,  which  spreads  out  in 
every  direction,  as  a  water-wave  does  when  water  is  forcibly 
disturbed  at  any  point.  In  the  latter  case  it  is  not  the 
water  which  moves,  except  slightly,  but  the  force  is  passed 
from  one  part  of  the  water  to  another,  and  thus  the  wave 
may  cross  an  ocean.  Just  so  the  force  or  impulse  travels 
in  the  rocks. 


Fig.  155.— Bends  in  a  railway  track  made  by  the  Charleston  earthquake. 

We  now  see  that  the  real  question  is.  What  is  the  force  ? 
When  an  earthquake  accompanies  a  volcanic  explosion  the 
same  force  evidently  causes  both — the  expansive  force  of 
steam.  In  other  cases  it  is  thought  that  the  forces  which 
lift  mountains  and  those  which  push  lavas  through  the 
crust  are  able  to  bend  or  strain  the  rocks,  and  the  straining 
gradually  increases  for  a  long  time,  until  at  last  there  is  a 
sudden  breaking,  which  gives  the  earthquake  impulse. 


CHAPTEE   X 

THE  ATMOSPHERE 

We  now  pass  from  the  forms  of  the  land  to  the  study  of 
the  Atmosphere,  which  covers  land  and  sea  and  has  much  to 
do  with  hoth.  The  word  means  vapor  hall^  and  is  thus  a 
good  name  for  the  envelope  of  the  globe.  It  lies  outside 
the  watery  sheet  which  so  nearly  covers  the  planet,  and  the 
water  in  turn  mantles  the  rocky  crust.  Thus  the  inner 
parts  of  the  earth  may  be  thought  of  as  having  three  covers 
— of  rock,  water,  and  air.  The  atmosphere  is  a  part  of  our 
globe,  and  not  merely  an  outside  blanket. 

197.  Composition  of  air. — Air  is  the  name  of  that  mix- 
ture of  gases  which  makes  up  the  atmosphere.  Before  we 
give  an  account  of  these  gases,  we  may  notice  certain  facts 
about  the  air.  As  it  has  neither  odor,  taste,  form,  nor 
color,  we  can  not  smell,  taste,  or  see  it.  We  feel  it  when  it 
is  in  motion  or  when  we  move  through  it,  and  we  notice 
keenly  whether  it  holds  much  or  little  heat.  Our  hearing 
depends  entirely  upon  wave  motions  which  spread  through 
it.  It  is  elastic,  and  expands  and  contracts  by  changes  of 
temperature,  and  when  pressure  is  withdrawn  or  applied. 
It  can  be  turned  into  liquid,  a  property  whose  importance 
may  prove  to  be  very  great.  It  is  essential  to  combustion 
as  well  as  to  the  slow  processes  of  decay,  and  is  required,  in 
larger  or  smaller  amounts,  by  all  animals  and  plants  (Sec. 
290). 

Air  is  made  up  chiefly  of  the  two  gases,  oxygen  and 
nitrogen,  in  the  proportion  of  one  part  of  the  former  to  four 
of  the  latter.  The  two  are  not  chemically  joined,  as  the 
16  333 


2M    AN  INTRODUCTIOK  TO   PHYSICAL  GEOGRAPHY 

hydrogen  and  oxygen  of  water,  but  are  mechanicaHy  mixed. 
To  stir  ashes  with  soil  would  roughly  illustrate  the  mingling 
of  the  invisible  molecules  of  oxygen  and  nitrogen.  The 
oxygen  is  the  active  element  in  burning,  in  decay,  and  in 
living  bodies.  It  unites  with  certain  substances  and  heat  is 
given  off.  If  this  process  goes  on  rapidly,  and  much  heat 
appears,  we  call  it  burning.  In  our  bodies  this  action  is 
constant  but  slower,  and  with  less  heat.  In  decay  the  pro- 
cess is  very  slow,  and  the  heating  is  correspondingly  little. 

The  nitrogen,  while  large  in  amount,  is  the  inactive 
element  in  the  air.  It  serves  to  dilute  the  active  oxygen, 
somewhat  as  strong  liquid  is  diluted  by  water.  Animals 
are  so  adjusted  to  this  constitution  of  the  air  that  any  great 
change  in  the  amount  of  oxygen  is  harmful  to  them. 

Carbon  dioxid,  often  called  carbonic  acid  gas,  is  a  com- 
bination of  carbon  and  oxygen.  It  is  present  in  the  air  in 
very  small  amount — about  0.03  of  one  per  cent — but  is  of 
great  importance.  Plants  take  it  in  through  the  leaves, 
break  it  up,  use  the  carbon  and  release  the  oxygen.  They 
also,  in  another  life  process,  give  off  carbon  dioxid,  but  on 
the  whole  they  receive  more  than  they  part  with,  and  the 
gas  is  a  food  on  which  they  are  dependent.  Animals 
breathe  in  oxygen,  and  give  off  carbon  dioxid.  When  we 
are  in  a  closed  room  our  breathing  continually  increases 
the  amount  of  carbon  dioxid  and  reduces  the  oxygen,  and 
if  this  is  kept  up  too  long  we  suffer  from  an  insufficient 
supply  of  oxygen.  For  this  reason,  and  because  harmful 
vapors  are  given  off  by  the  body,  the  ventilation  of  sleep- 
ing and  living  rooms  is  important.  Certain  other  gases  are 
in  the  air  in  very  small  amounts,  but  we  need  not  concern 
ourselves  with  them. 

The  vapor  of  water  is  always  present,  but  the  quantity 
is  very  variable.  It  is  gathered  by  evaporation,  mainly 
from  the  ocean,  is  floated  everywhere  by  the  winds,  as  rain 
it  waters  the  fields  and  forms  the  rivers.  All  the  life  of  the 
land  depends  upon  it,  and  the  forms  of  the  land  also,  as 


THE  ATMOSPHERE  225 

molded  by  solution,  river,  and  glacier.  In  later  sections  we 
shall  study  Humidity,  Dew,  Frost,  Clouds,  and  Eainfall. 
All  these  topics  relate  to  moisture  in  the  air. 

Fine  dust  is  everywhere  present,  especially  in  the  lower 
levels  of  the  atmosphere.  It  is  not  a  part  of  the  air,  but 
floats  within  it.  We  can  sometimes  see  its  particles  when  a 
beam  of  sunlight  enters  a  poorly  lighted  room.  The  haze 
following  great  forest  fires,  and  the  pall  often  hanging  over 
manufacturing  cities,  are  due  to  dust.  All  man's  operations 
cast  more  or  less  dust  into  the  air.  The  winds  blow  fine 
plant  and  mineral  fragments  up  from  the  forests,  roads,  and 
fields  (Chapter  V),  and  explosive  volcanic  eruptions  scatter 
dust  widely.  When  heavy  rains  follow  a  period  of  drought, 
the  dust  is  washed  from  the  air,  and  we  say  that  the  air  is 
cleared.  When  rain-water  is  gathered  in  tanks  and  cisterns, 
some  of  the  dust  appears  as  sediment.  Not  least  important 
are  the  minute  living  things  which  are  always  found  in  the 
air,  and  may  be  blown  to  long  distances.  Such  are  seeds 
and  the  pollen  of  flowers,  and  especially  the  microscopic 
germs  of  many  diseases. 

198.  Weight  and  height  of  the  atmosphere. — Air,  though 
a  mixture  of  gases,  is  a  material  substance,  as  is  well  shown 
by  forcing  it  into  liquid  form.  It  has  weight,  therefore, 
though  much  less  than  a  liquid  or  solid.  In  the  space  of  a 
cubic  foot  there  is  more  than  an  ounce  of  air,  and  an  ordi- 
nary school-room  contains  several  hundred  pounds.  Be- 
cause of  its  weight,  air  pushes  downward,  pressing  on  the 
ground  and  the  ocean.  The  upper  part  of  the  atmosphere 
also  presses  on  the  lower  part.  Though  the  atmosphere  is 
really  not  separated  into  parts,  we  can  think  of  it  as  com- 
posed of  horizontal  layers,  resting  one  on  another,  and  thus 
compare  it  to  a  pile  of  boards.  Just  as  each  board  bears 
the  weight  of  all  the  boards  above  it,  so  each  layer  of  air  is 
pressed  upon  by  the  weight  of  all  the  air  above  it.  The 
boards  are  unyielding,  but  the  elastic  air  is  crowded  together 
by  the  pressure — like  a  dry  sponge  or  a  coiled  spring.    The 


226    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


20 


greater  the  pressure,  the  more  the  air  is  packed  together. 
So  low  layers  of  air,  sustaining  great  weight,  are  compara- 
tively dense,  and  high  layers,  sustaining  less  weight,  are 
comparatively  thin  or  rare.     There  is  a  gradual  thinning 

^  from  the  level  of  the   sea 

!  I  upward;   about  the   top   of 

I  Mount  St.  Elias  the  air  is 

only  half  as  dense  as  about 
its  base.  Therefore,  on  a 
high  mountain  the  lungs 
get  less  air  at  each  breath, 
and  one  must  breathe  quick- 
ly to  keep  them  supplied. 
A  very  little  exertion  makes 
one  pant  violently. 

In  the  first  few  miles  of 
ascent  the  air  thins  more 
rapidly  than  at  greater 
heights,  and  the  change 
finally  becomes  very  gradu- 
al. Reasons  have  been  found 
for  feeling  sure  that  very 
thin  air  exists  at  the  height 
of  a  hundred  miles.  How 
much  farther  out  into  space 
the  last  scanty  remnant  of 
our  atmosphere  reaches  may 
never  be  known.  By  far  the  greater  part  of  it,  as  measured 
by  weight,  lies  below  the  level  of  the  highest  mountain  tops 
(see  Fig.  156). 

199.  Humidity. — This  is  a  scientific  term  which  is  also 
much  used  in  common  speech  in  referring  to  the  moisture 
of  the  atmosphere.  If  there  is  much  moisture  we  say  that 
the  humidity  is  great.  In  warm  weather  the  air  is  heavy 
and  lifeless,  and  we  call  the  day  or  the  night  sultry.  In 
addition  to  the  depressing  effect,  we  perspire  freely.     Mois- 


FiG.  156.— Diagram  of  the  atmosphere. 
Varying  depth  of  shade  indicates 
varying  density.  The  highest  peak 
corresponds  to  the  Himalaya,  the 
lower  peaks  to  the  Sierra  Nevada 
and  Kooky  Mountains. 


THE  ATMOSPHERE  227 

ture  is  always  escaping  from  the  pores  of  the  skin,  but  in 
dry  weather  it  evaporates.  Warm  and  humid  air  about  us 
is  like  a  filled  sponge,  refusing  to  absorb  more,  hei^ce  the 
drops  gather  on  the  body.  If  the  air  is  cold  and  humid,  it 
brings  chill  and  a  cutting  sensation  upon  exposure.  In 
dry,  hot  days  the  air  is  like  an  empty  sponge — it  absorbs 
readily,  plants  lose  their  moisture  through  the  leaves  and 
wilt,  washed  clothes  dry  rapidly,  and  we  say  the  humidity 
is  low. 

The  warmer  the  air,  the  more  water  vapor  it  can  hold. 
The  sun's  heat,  falling  on  the  sea,  on  rivers,  and  on  moist 
earth,  causes  evaporation.  If  the  air  has  thus  taken  in  all 
the  vapor  it  can  hold  at  a  particular  temperature,  and  the 
temperature  be  lowered,  some  of  the  invisible  particles  will 
fly  together — that  is,  condensation  will  take  place — and 
there  will  be  fog,  clouds,  dew,  rain,  or  snow.  Thus  the 
atmosphere  is  always  receiving  water  in  some  places  and 
yielding  it  up  in  others. 

If  air  at  a  temperature  of  75°  (or  any  other  degree)  has 
all  the  vapor  it  can  hold,  it  is  said  to  be  saturated.  Its 
vapor  contents  exactly  equal  its  capacity  for  vapor,  and 
hence  the  relative  humidity  is  said  to  be  100  per  cent.  If 
the  same  air  were  filled  to  only  half  its  capacity,  the  rela- 
tive humidity  would  be  50  per  cent.  If  now  we  gradually 
lower  the  temperature,  but  keep  the  amount  of  water  the 
same,  we  come  at  last  to  the  point  of  saturation,  and  the 
relative  humidity  becomes  100  per  cent,  instead  of  50  per 
cent.  Eelative  humidity  does  not  tell  us  how  much  water 
there  is  in  the  air,  but  it  gives  the  ratio  of  the  moisture 
present,  to  that  which  the  air  at  that  temperature  is  able 
to  hold. 

200.  Dew  and  frost. — As  night  comes  on  the  sun's  heat 
is  removed,  the  air  grows  cool,  especially  near  the  ground ; 
its  ability  to  hold  moisture  decreases,  and  it  may  become 
saturated — that  is,  the  relative  humidity  may  become  100 
per  cent.     If  now  the  temperature  continues  to  go  down, 


228    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

the  vapor  wiH  condense  and  be  found  on  grass  and  leaves, 
and  even  sometimes  on  roofs  and  stones.  This  is  Dew. 
The  temperature  at  which  it  begins  to  form  is  known  as 
the  Dew-point. 

When  the  air  is  comparatively  dry  (relative  humidity 
low),  and  the  drop  in  temperature  is  slight,  there  will  be 
no  dew,  the  point  of  saturation  not  being  reached.  Dew  is 
not  apt  to  be  formed  on  cloudy  nights,  because  the  clouds 
prevent  the  rapid  cooling  of  the  ground.  It  will  be  under- 
stood that  the  dew  does  not  really  "  fall,"  but  gathers  by 
direct  contact  with  moist  air. 

If  the  surplus  moisture  from  the  air  or  from  the  ground 
condenses  at  temperatures  below  the  freezing-point  we 
have  white  frost,  or  "  hoar  "  frost,  instead  of  dew.  It  is 
most  noticeable  in  autumn  and  spring  upon  roofs,  fences, 
and  fields.  Clouds  often  prevent  frost  by  holding  in  the 
heat  which  has  accumulated  during  the  day,  and  we  some- 
times imitate  nature  by  covering  plants  on  clear  nights  to 
protect  them  from  frost. 

201.  Clouds  and  fog. — Fog  is  a  cloud  in  the  lower  air. 
If  the  dew-point  is  reached  at  the  earth's  surface,  moisture 
gathers  there.  If  a  few  feet  or  a  few  hundred  feet  of  the 
lower  air  cool  to  the  dew-point,  fog  is  formed.  The  par- 
ticles of  invisible  vapor  unite  and  become  visible,  but  are 
still  so  small  that  the  air  supports  them.  Thus  it  is  that  a 
thin  layer  of  mist  may  spread  over  a  swamp  or  valley  bot- 
tom, so  that  from  a  hilltop  we  can  look  out  over  a  lake  of 
fog.  In  the  rays  of  the  sun  the  air  grows  warmer,  and 
when  the  relative  humidity  falls  below  100  per  cent  the 
fog  evaporates. 

The  particles  of  vapor  separate  more  readily  from  the 
air  when  they  can  at  the  same  time  attach  themselves  to 
particles  of  dust.  It  is  also  true  that  the  floating  dust 
cools  faster  than  the  air  about  it,  just  as  the  ground  cools 
faster  than  the  neighboring  air.  For  these  reasons  the  for- 
mation of  fog  begins  by  the  gathering  of  minute  spheres  of 


Fig.  157.— Cirrus  clouds. 


Fig.  158.— High  cumulus  clouds. 


^^^^^ 

b 

^^^iiM 

'H4l^^i^*' 

i%^ifflrf  AMMi  " 

Fig.  ]69.— Low  cumulus  clouds. 


229 


230    AN   INTRODUCTION  TO   PHYSICAL  GEOGRAPHY 

water  about  still  smaller  particles  of  dust,  and  the  densest 
fogs  occur  where  the  air  contains  much  fine  dust. 

Clouds  are  not  different  from  fogs  except  that  they  are 
higher  in  the  air.  If  we  ascend  a  mountain  which  is 
wrapped  in  cloud,  we  find  ourselves  enveloped  in  fog. 
Clouds  are  caused  by  condensation  resulting  from  the  cool- 
ing of  the  air.  The  cooling  may  be  brought  about  in  vari- 
ous ways,  but  is  usually  occasioned  by  an  upward  movement 
of  air.  So  also  clouds  are  sometimes  dissolved  when  air  is 
warmed  by  downward  movement.  We  shall  see  how  the 
rising  and  sinking  of  bodies  of  air  make  them  cooler  and 
warmer  when  we  study  the  sections  (207-216)  on  heat  and 
temperature. 

A  little  watching  of  clouds  will  show  us  that  we  can 
divide  them  roughly  into  classes  by  their  form.  Ascend- 
ing currents  of  moist  air  cool,  condense,  and  roll  up  moun- 
tainous masses  of  cloud,  having  a  height  of  thousands  of 
feet  or  sometimes  of  several  miles.  Whether  large  or  small, 
they  are  known  as  Cumulus  clouds.  Their  bases  are  hori- 
zontal, and  mark  the  level  at  which  the  rising  air  is  cooled 
to  the  dew-point  so  that  condensation  begins.  Great 
cumulus  clouds,  growing  rapidly  in  height,  are  often  seen 
in  summer  in  connection  with  thunder-storms.  They  are 
popularly  spoken  of  as  "  thunder  heads."  Tangled  and 
feathery,  delicate  and  plume-like  clouds  are  called  Cirrus. 
They  are  the  highest  clouds,  usually  from  5  to  10  miles 
above  the  sea  level,  and  they  are  thin,  obstructing  but 
slightly  the  passage  of  the  sun's  rays.  Any  widely  spread 
cloud  mass  from  which  rain  or  snow  is  falling  may  be 
called  Nimbus,  and  the  name  Stratus  is  sometimes  applied 
to  horizontal  layers  of  cloud. 

202.  Rain  and  snow.— Everything  that  moves  through 
the  air  rouses  a  resistance  called  friction.  Heavy  bodies 
are  less  checked  by  this  friction  than  light  bodies.  The 
minute  water  particles  forming  clouds,  like  the  particles  of 
gne  dust^  have  so  little  weight  that  their  falling  is  exceed- 


THE  ATMOSPHERE  231 

ingly  slow,  and  we  say  they  float  in  the  air.  If  the  con- 
densation that  made  them  is  carried  farther  they  grow 
larger,  fall  faster,  gather  still  more  moisture  as  they  de- 
scend through  moist  air,  and  come  down  as  Kain. 

If  condensation  takes  place  in  a  region  whose  tempera- 
ture is  below  the  freezing-point,  the  moisture  gathers  into 
crystals  of  ice  of  various  forms,  and  these  fall  as  Snow. 
Flakes  of  snow  are  related  to  drops  of  rain  as  hoar  frost  is 
to  dew.  When  a  cloud  in  which  rain-drops  are  forming  is 
at  the  same  time  cooled  below  32°,  the  drops  are  frozen  to 
ice  pellets.  Sometimes  these  pellets,  by  falling  through 
freezing  rain,  or  rain  and  snow,  gather  more  ice  and  become 
hailstones,  and  these  are  often  large  enough  to  reach  the 
earth  without  melting. 

203.  Rainfall. — This  term  is  applied  to  all  descent  of 
water  to  the  earth's  surface,  whether  as  rain,  snow,  or 
hail.  It  relates  to  the  quantity  of  the  downfall.  The  word 
Precipitation  is  also  used  in  this  sense.  As  we  shall  see 
in  Chapter  XI,  the  rainfall  of  a  region  is  one  of  the  most 
important  elements  of  its  climate.  When  snow  falls  in 
still  weather  it  makes  an  even  layer  on  the  ground,  and  we 
can  measure  its  depth  in  inches  or  feet.  But  as  snow  may 
be  wet  and  heavy  or  dry  and  light,  such  measurement  does 
not  tell  how  much  water  the  snow  represents.  Therefore, 
for  exactness,  the  snow  resting  on  a  definite  space — a 
square  foot,  for  example — is  melted,  and  the  resulting  water 
is  measured.  To  learn  the  amount  of  rain  which  falls,  a 
vessel  like  a  bucket,  with  straight  sides,  is  placed  out  of 
doors,  and  after  each  rain  the  depth  of  the  water  caught 
in  it  is  measured.  The  quantity  of  rainfall  at  any  place  or 
in  any  time  is  expressed  in  inches  of  depth. 

The  map  of  the  United  States  in  Fig.  160  shows  by 
shades  of  blue  the  amount  of  rainfall  during  a  year  in  dif- 
ferent parts.  For  example,  a  shade  made  by  parallel,  slant- 
ing lines  covers  all  districts  in  which  the  rainfall  is  more 
than  30  inches  and  less  than  40  inches.     There  is  a  "  scale 


232    AN  INTRODUCTION  TO   PHYSICAL  GEOGRAPHY 

of  shades  "  to  show  what  each  pattern  stands  for,  and  with 
its  help  any  part  of  the  map  can  be  read.  The  map  should 
be  carefully  studied  not  only  because  of  the  information  it 
gives  about  rain,  but  because  it  is  an  example  of  an  im- 
portant mode  of  combining  many  facts  into  a  sort  of  picture 
easily  understood.  Such  a  map  is  said  to  show  the  Geo- 
graphic Distribution  of  rainfall.  Instead  of  rainfall,  colors 
and  shades  may  be  made  to  stand  for  temperatures,  or  soils, 
or  population,  or  anything  else  having  a  geographic  arrange- 
ment. 

A  narrow  belt  along  the  sea  in  Oregon  and  Washington 
receives  more  than  60  inches  of  rainfall  in  a  year.  In  places 
in  the  latter  State  the  amount  is  a  little  more  than  100 
inches.  The  west  winds  from  the  warm  Pacific,  laden  with 
vapor,  are  chilled  to  the  dew-point  as  they  begin  their  jour- 
ney over  the  cooler  land.  Similar  abundant  rains  occur  in 
part  of  Florida,  and  the  rainfall  of  all  the  States  bordering 
the  Gulf  of  Mexico  and  the  Atlantic  Ocean  is  in  general 
more  than  50  inches  per  year. 

On  the  other  hand,  there  are  districts  in  Nevada,  south- 
ern California,  and  Arizona  where  the  rainfall  is  less  than 
5  inches  a  year ;  and  over  most  of  Xevada  and  Utah,  with 
parts  of  Arizona,  New  Mexico,  Colorado,  and  Wyoming,  the 
amount  is  below  10  inches  a  year.  A  still  wider  belt,  reach- 
ing from  middle  Oregon  far  into  Nebraska  and  southward, 
has  less  than  20  inches.  Here  is  the  great  arid  region  of 
the  United  States.  The  moist  air  from  the  ocean  loses 
much  of  its  moisture  in  passing  the  mountains  of  the 
coastal  belt,  especially  at  the  north,  and  has  little  rain  to 
distribute  in  the  interior.  The  Rocky  Mountains  receive 
much  more  of  this  remnant  than  the  plateaus  on  either 
hand. 

In  southern  California,  Lower  California,  and  northern 
Mexico  the  arid  region  extends  to  the  very  coast  of  the 
Pacific  Ocean,  the  explanation  being  found  in  the  compara- 
tive warmth  of  the  land  as  compared  to  the  ocean.     Tliis 


THE  ATMOSPHERE  233 

leads  to  the  principle  that  mere  nearness  to  the  ocean  does 
not  cause  abundant  rain  unless  the  air  from  the  ocean 
grows  cooler  in  crossing  the  land.  If  the  ocean  is  cooler 
than  the  adjacent  land,  then  whatever  winds  blow  from 
ocean  to  land  have  their  capacity  for  moisture  increased  by 
warming,  and  instead  of  dropping  rain,  drink  up  any  water 
they  find. 

The  northern  Mississippi  region  receives  a  medium 
amount  of  rain.  It  has  enough  to  support  abundant  vege- 
tation, but  less  than  the  regions  adjoining  the  Gulf  or  cither 
ocean.  This  brings  out  another  great  principle :  that  rain- 
fall is  less  abundant  in  the  interior  of  continents  than  it 
is  upon  their  borders.  Such  lands  are  farther  from  the 
source  of  supply. 

If  we  go  south  we  shall  find  very  great  rainfall  in  some 
parts  of  Central  America,  and  in  the  northern,  central,  and 
eastern  parts  of  South  America.  Much  of  the  Amazon 
country  receives  over  80  inches.  The  prevailing  winds 
from  the  warmest  part  of  the  Atlantic  explain  this  condi- 
tion, which  is  the  great  exception  to  the  rule  of  small  rain- 
fall in  the  centers  of  continents.  We  may  now  say  that, 
as  a  rule,  rains  are  more  abundant  in  the  tropical  latitudes, 
but  there  are  exceptions  to  this  principle,  as  some  parts  of 
South  America,  west  of  the  Andes,  are  very  dry.  We  may 
also  observe  that  in  polar  latitudes  the  rainfall  (mainly  as 
snow)  is  less  than  in  temperate  and  tropical  regions,  be- 
cause these  regions  are  too  cold  for  much  water  to  be  evap- 
orated from  the  seas. 

The  rainfall  of  Great  Britain  and  Ireland  (Fig.  161)  gives 
us  an  interesting  parallel,  on  a  small  scale,  with  the  western 
United  States.  The  moisture-bearing  winds  come  from  the 
Atlantic,  and  the  western  coasts  have  40  inches  of  rainfall, 
with  60  to  80  inches  on  the  highlands,  but  the  central  and 
eastern  plains  have  only  25  to  30  inches.  In  a  hot  region 
25  inches  of  rain  would  be  a  meager  supply  for  farm  or 
garden,  but  in  the  cool  climate  of  England  it  is  ample.     As 


23  i    AN  INTRODUCTION  TO   PHYSICAL  GEOGRAPHY 


we  go  eastward  over  the  plains  of  Europe,  we  find  the  rain- 
fall gradually  less,  and  much  of  Russia  is  arid — further  illus- 
trating the  principle  that  the  interior  of  a  continent  is  drier 

than  its  borders.  In  south- 
ern Europe  the  Alps  re- 
ceive abundant  moisture, 
brought  by  warm  winds 
from  the  evaporating  sur- 
face of  the  Mediterranean. 
The  rainfall  of  Asia 
shows  the  usual  contrasts 
between  the  sea  border  and 
interior,  and  between  trop- 
ical and  arctic  latitudes. 
Thus,  in  India  and  Burma, 
the  southwest  monsoons 
(Sec.  224and  Fig.  182)  from 
the  Indian  Ocean  bring 
great  rains,  and  southern 
Asia  is  well  watered  up  to 
the  Himalaya  Mountains. 
Amid  their  cold  heights 
the  moisture  which  has 
been  successfully  carried 
over  the  plains  of  India  is  condensed,  and  the  high  plateaus 
of  Tibet  and  of  central  Asia  in  general  are  a  desert.  South- 
ern Siberia  receives  moderate  rainfall,  but  the  north  is 
dry,  even  though  bordering  the  Arctic  Sea,  for  the  reason 
already  stated,  that  little  evaporation  can  take  place  where 
winter  continues  for  most  of  the  year. 

Eastern  Asia  has  a  plentiful  supply  of  rain.  Japan  has 
a  rainy  season  lasting  most  of  the  time  from  April  until 
September.  The  average  fall  at  Tokio  is  58  inches.  This 
resembles  in  abundance  that  of  western  AYashington  and 
the  Florida  coast  in  our  own  country.  At  the  capital  of 
Korea  the  rainfall  averages  36  inches,  but  at  Hongkong, 


Fig.  161.— Rainfall  map  of  the  British  is- 
lands. The  country  with  more  than  20 
and  less  than  40  inches  is  shaded  by 
oblique  lines  ;  that  with  between  40  and 
60  inches,  by  vertical  parallel  lines ;  with 
between  60  and  80  inches  by  crossed 
lines  ;  with  more  than  80  inches,  by  solid 
black.    (See  page  233.) 


THE  ATMOSPHERE 


235 


much  farther  south  and  directly  affected  by  the  sea,  the 
amount  is  78  inches.  Similarly  heavy  is  the  rainfall  of  the 
Philippine  Islands  and  the  Dutch  East  Indies.  The  most 
wonderful  rainfall  in  the  world  is  found  where  the  monsoon 
winds  from  the  Indian  Ocean  send  down  their  moisture 
upon  the  delta  region  of  the  Ganges,  resulting  in  an  average 
fall  of  500  inches  a  year,  and  amounting  in  one  exceptional 
year  to  800  inches,  which,  if  it  could  have  remained  on  the 
surface,  would  have  formed  a  sea  67  feet  deep. 


\                       * 

120  ln.P2*^--r---------'^ 

iJiJiiiiJiirflt 

m 

-:-z--:--:<--yz--y,^^m 

^^^mL      / 

mm       X. 

-■"-■^-^----s--'^:^^^ 

^K^' 

fe>-z-.=55zz- 

z-vz- --^^^^^^^^^^  hi/ 

^-l--3Sz^i"^z^: 

=^ft^H[ 

^^^ 

^^^m" 

^W^K 

io^ ^0^ .^ u-'T                                                        ___J 

Fig.  162.— Rainfall  map  of  Australia.  Dotted  lines  run  through  points  of  equal  rain- 
fall. The  country  with  more  than  5  and  less  than  20  inches  rainfall  is  shaded  by 
broken  horizontal  lines  ;  that  with  between  20  and  40  inches,  by  oblique  lines  ; 
with  more  than  40  inches,  by  vertical  lines. 

Australia  (Fig.  162)  has  an  enormous  interior  area  with 
rainfall  of  less  than  10  inches.  In  a  general  way,  this  in- 
creases toward  the  shore  line,  though  parts  of  the  south 
and  west  coast  are  dry.  The  north  and  east  coast  areas 
have  from  30  up  to  50  inches  or  more.     We  still  find  our 


236     AN  INTRODUCTION  TO   PHYSICAL  GEOGRAPHY 

principle  of  a  dry  interior  and  a  wet  border  true  for  the 
great  lands. 

The  largest  dry  area  in  the  world  is  the  Sahara  of  North 
Africa.  The  general  movement  of  air  across  it  is  from  the 
Mediterranean  at  the  north,  and  this  air,  passing  from  a 
relatively  cool  ocean  to  a  very  warm  land,  refuses  to  give  up 
its  water.  The  same  principle  controls  as  in  southern  Cali- 
fornia. 

Light  and  Color 

204.  Light. — The  light  which  comes  to  us  from  the  sun 
travels  in  a  straight  line,  and  with  such  wonderful  speed 
that  it  reaches  the  earth  in  about  eight  minutes.  It  is 
white,  and  we  commonly  say  it  is  without  color,  but  the 
absence  of  color  is  really  black,  and  white  is  the  sum  of  all 
colors.  A  beam  of  white  sunlight  is  made  up  of  a  great 
number  of  variously  colored  rays  —  red,  orange,  yellow, 
green,  blue,  violet.  The  full  understanding  of  the  nature 
of  light  belongs  to  the  subject  of  physics,  but  we  need 
to  know  a  few  of  its  properties,  in  order  to  study  the  sky 
intelligently. 

There  are  three  ways  in  which  white  light  is  divided 
into  the  colors  which  compose  it :  (1)  When  it  falls  on  an 
object  which  is  neither  white  nor  black,  some  of  the  rays 
are  absorbed  and  disappear  while  others  are  Eeflected. 
Thus  grass  reflects  the  green  rays  and  a  lemon  the  yellow 
rays.  (2)  When  sunlight  passes  from  one  transparent  sub- 
stance to  another  its  rays  are  usually  bent  or  Eefracted, 
and  some  rays  are  bent  more  than  others.  Thus  if  a  nar- 
row beam  of  light  is  allowed  to  pass  through  a  glass  prism 
to  a  sheet  of  white  paper,  the  red  rays  reach  the  paper  in 
one  place,  the  yellow  in  another,  the  blue  in  another,  and 
we  have  a  beautiful  series  of  color-bands.  (3)  And  when 
light  is  sifted  through  a  thin  cloud  of  very  fine  particles  it 
is  scattered  by  Diffraction,  the  several  colors  being  differ- 
ently affected  and  thus  separated.     Nearly  all  the  beautiful 


THE  ATMOSPHERE  237 

and  infinitely  varied  colors  of  nature  are  produced  in  some 
one  of  these  ways. 

205.  Colors  of  the  sky. — AVe  have  already  learned  that 
the  atmosphere  carries  small  particles  picked  up  by  the 
wind.  The  finest  of  these  are  so  minute  as  to  be  invisible ; 
they  float  so  high  as  to  be  above  all  rain  and  are  never 
washed  out.  Their  existence  is  known  only  by  their  effect 
on  sunlight,  which  they  scatter  enough  to  give  color  to  the 
sky.  Without  the  dust  a  cloudless  sky  would  be  black. 
With  it  all  the  upper  part  is  blue,  changing  to  pale  gray 
near  the  sun  and  near  the  horizon,  while  at  sunset  and 
sunrise  the  blue  grades  downward  into  rich  yellow  and 
rose,  orange  and  red.  Little  wonder  is  it  that  the  sky  is 
thought  by  savage  peoples  to  be  a  solid  dome  of  crystal. 

When  the  lower  air  contains  coarser  dust,  or  haze,  all 
the  colors  become  duller,  and  grays  predominate  ;  but  what 
may  be  called  water-dust — the  minute  particles  of  vapor  at 
the  edges  of  clouds — give  at  sunset  the  most  intense  of  all 
sky  colors.  The  great  explosion  of  Krakatoa  in  1883  sent 
an  immense  cloud  of  fine  dust  into  the  upper  air,  which 
gradually  drifted  and  spread,  intensifying  the  sunset  effects 
wherever  it  went.  Within  a  year  it  had  covered  the  whole 
globe,  and  it  settled  from  the  air  so  slowly  that  some  of  its 
effects  were  still  visible  three  years  later. 

206.  The  rainbow. — This  is  an  arch  showing  the  colors 
given  by  the  prism.  It  is  seen  where  the  sun  shines  on 
drops  of  falling  water.  It  most  often  appears  after  a 
thunder-shower  has  passed,  but  on  a  small  scale  may  be 
seen  in  the  spray  of  a  waterfall  or  even  an  artificial  spray. 
In  each  drop  of  water  the  sun^s  rays  are  bent  (refracted), 
turned  back  (reflected),  and  bent  again,  and  the  white  light 
is  broken  up  into  its  constituent  colors.  The  rainbow  is 
not  seen  in  widely  extended  rains,  because  the  clouds  then 
cut  off  the  sunlight. 

A  halo  is  a  ring  of  light  about  the  sun  or  moon,  and  is 
believed  to  be  due  to  similar  action  of  the  light  rays  upon 


238    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

very  small  ice  crystals,  forming  thin  clouds  in  the  upper 
regions  of  the  atmosphere. 

Temperature  of  the  Atmosphere 

207.  Measii5renient  of  temperature. — This  is  done  more  or 

less  carefully  by  almost  every  one  in  civilized  lands.     The 

instrument  is  the  Thermometer  (from  two 

Cent-  Fahr-  \ 

^  Greek  words  meaning  warm  and  measure). 

A  small  fflass  tube,  of   uniform  size,  has  a 

200"  <=}  '  y 

190*        bulb  at  one   end  which  is  filled  with  some 

180* 

way  up  the  tube.     If  the  mercury  is  warmed 


:i.2l2 


_^^.        liquid,  usually  mercury,  which  extends  part 

E-  160° 

|^°.        it  expands,  some  of  it  passes  from  the  bulb 


'30  to  the  tube,  and  the  column  of  mercurv  in 

120 

110*  the  tube  grows  longer.      If  the  mercury  is 

,  '°°  cooled  the  column  becomes  shorter.     Thus 

'—  00 

so]  the  position  of  the  top  of  the  column  de- 

t.  6°-  pends  on  the  degree  of  warmth,  or  the  Tem- 

hso]  perature,  of   the  mercury.      To  each  ther- 


30*        mometer  a  scale  of  parts  is  attached.     Eng- 

20* 
10° 


lish  -  speaking   peoples  use   mainly  what  is 

Zero.       known  as  the  Fahrenheit  scale,  on  which 

]2°o«        the  temperature  at   which  water  freezes  is 

-30*        marked  as  32°,  and  the  temperature  at  which 

water  boils  as  212°.    In  many  other  countries 

„     ^  the   Centigrade  scale  is  used,  in  which   0° 

Fig.  163.— A  ther-  ,         ,         «  .  .  t     -,       o  n        i      m 

mometer      with  marks  the  freczmg-point  and  100    the  boil- 
Fahrenheit    and  inor-point  of  watcr.     As  180  degrees  of  one 

Centigrade  scales.        %^  ^,  %  _  _    , 

scale  covers  the  same  range  as  100  degrees 
of  the  other,  their  degrees  have  not  the  same  size.  One 
degree  of  the  centigrade  scale  equals  1.8  degree  of  the 
Fahrenheit.     In  this  book  the  Fahrenheit  scale  is  used. 

To  measure  the  temperature  of  the  air  the  thermometer 
is  hung  where  it  will  not  be  affected  by  heat  radiated  from 
other  objects,  especially  the  sun  and  the  human  body,  and 
allowed  to  remain  a  few  minutes  until  the  air  has  had  time 


THE  ATMOSPHERE  239 

to  cool  or  warm  the  mercury  to  its  own  temperature.  Then 
the  top  of  the  mercury  column  is  compared  with  the  scale, 
and  the  mark  it  stands  nearest  is  noted.  This  is  called 
"  reading  the  thermometer  "  or  "  observing  the  tempera- 
ture." 

208.  Source  of  heat  in  the  atmosphere. — We  may  neglect 
the  small  amount  that  comes  from  the  stars.  So  also  we 
may  leave  out  of  account  any  heat  from  the  earth's  interior. 
The  cold  crust  lets  little  heat  come  through,  except  locally 
in  volcanic  eruptions  and  hot  springs.  Practically  all  at- 
mospheric warmth  comes  from  the  sun.  As  the  earth  is  only 
a  speck,  far  from  the  sun,  and  the  sun  blazes  out  in  all 
directions,  we  receive  only  an  inconceivably  small  fraction 
of  the  sun's  total  heat.  But  without  it  the  earth  would  be 
a  frozen,  dark,  and  lifeless  ball. 

209.  Modes  of  warming  and  cooling. — Place  a  brick  on  a 
hot  stove.  After  it  has  been  there  a  few  minutes  lift  it  for 
a  moment  and  feel  the  under  surface.  It  is  warm.  It 
has  become  warm  by  receiving  heat  from  the  iron  of  the 
stove.  You  know  that  it  is  warm  because  it  communicates 
heat  to  your  hand.  Such  transfers  of  heat  are  called  Con- 
duction. Conduction  may  also  take  place  within  a  body ; 
leave  the  brick  on  the  stove  for  an  hour,  and  the  heat  will 
be  conducted  through  it  so  that  the  top  as  well  as  the  bottom 
will  be  hot.  Xow  set  the  hot  brick  away  from  the  stove, 
and  then  bring  your  hand  near  it.  Without  touching  it 
you  feel  its  heat.  This  is  because  the  brick  is  losing  heat 
by  Radiation ;  your  hand  receives  some  of  its  rays  and  is 
warmed.  In  time  it  will  radiate  away  all  the  heat  it  gained 
from  the  stove  and  be  as  cool  as  the  air  about  it.  Try  yet 
another  experiment.  Bring  your  hand  near  a  block  of  ice. 
Your  hand  is  cooled  because  it  radiates  heat  to  the  ice. 
Take  the  ice  in  your  hand  and  the  hand  soon  becomes 
unpleasantly  cold  ;  the  heat  is  now  passing  from  it  by  con- 
duction. All  bodies  have  some  heat,  but  there  are  differ- 
ences in  quantity.     The  important  principle  is  that  heat 

17 


240    AN  INTRODUCTION   TO  PHYSICAL  GEOGRAPHY 

constantly  tends  to  pass,  by  conduction  and  radiation,  from 
warmer  to  cooler  bodies.    We  are  now  ready  to  understand — 

210.  How  the  sun  warms  the  atmosphere. — The  sun's 
rays,  falling  all  day  on  the  ground  and  the  ocean,  warm 
them.  The  ground  and  ocean,  because  they  are  warm, 
radiate  heat  outward.  Both  radiations  pass  through  the 
air,  and  the  air  is  warmed  by  them.  The  amount  of  heat 
received  by  the  air  directly  is  small,  but  the  dust  and  cloud 
particles  absorb  heat  more  freely  than  the  gases,  and  much 
that  they  receive  is  given  to  the  air  about  them.  The  air 
is  also  warmed  by  contact  with  the  warm  ground. 

At  night  the  outward  radiation  by  ground  and  ocean, 
cloud  and  dust,  is  not  balanced  by  the  sun's  radiation  and 
there  is  a  general  cooling.  The  change  in  temperature 
from  day  to  night  and  night  to  day  is  small  in  the  upper 
air  and  greatest  at  the  ground.  So  the  ground  at  night 
usually  cools  the  low-lying  air  instead  of  warming  it. 

Clouds  intercept  radiation  whether  from  above  or  be- 
low. So  when  a  dense  canopy  spans  all  the  sky  the  ground 
is  little  warmed  in  the  day  and  little  cooled  at  night,  and 
the  lower  air,  with  which  we  are  most  concerned,  under- 


PiG.  164.— When  the  sun  is  high  in  the  sky  the  course  of  its  rays 
through  the  air  is  shorter  than  when  it  is  near  the  horizon. 


goes  little  change.  So,  too,  haze  protects  the  ground  and 
the  lowest  air  from  extreme  changes  ;  but  the  hazy  air 
itself  is  warmed  and  cooled  more  than  clear  air  would  be. 
It  is  when  the  sky  is  clearest  that  we  feel  the  greatest 
changes  in  the  warmth  of  the  air.  In  clear  weather  come 
the  hottest  days  of  summer,  the  latest  frosts  of  spring,  and 


THE  ATMOSPHERE 


241 


the  earliest  frosts  of  autumn.  The  sun's  rays  do  not  seem 
so  warm  in  early  morning  and  late  afternoon  as  they  do  in 
the  middle  of  the  day ;  and,  in  fact,  they  carry  less  heat 
then,  for  they  have  lost  more  in  passing  through  the  air. 
Fig.  164  shows  this.  The  curve  through  A  stands  for  the 
earth's  surface,  the  curve  close  to  it  for  the  upper  limit  of 
clouds,  and  the  upper  curve  for  the  outer  limit  of  the 
atmosphere.  Suppose  we  are  at  A.  When  the  sun  is 
low  in  the  sky  the  rays  that  reach  us  pass  through  much 
more  air  {D  to  A)  than  when  the  sun  is  high  (^  to  ^)  ; 
and  the  difference  is  still 
greater  (^  to  A,  com- 
pared with  C  to  A)  in 
respect  to  the  denser  air 
which  absorbs  most  heat. 
In  the  warming  of  the 
ground  there  is  another 
difference  also,  for  a 
slanting  beam  spreads  its 
warming    effect   over    a 

larger  surface  than  a  vertical  beam  of  the  same  size  (Fig. 
165),  and  even  if  it  had  the  same  total  amount  of  heat  to 
bestow,  could  give  less  to  each  square  foot  of  surface. 

211.  Temperature  of  day  and  night. — We  have  just  seen 
that  the  sun  warms  the  air  most  when  it  is  highest  in  the 
sky,  and  that  is  at  noon ;  but  the  warmest  part  of  the  day 
is  usually  several  hours  later.  This  is  because  heat  is  ac- 
cumulated. The  air  about  us  is  all  the  time  receiving  heat 
in  various  ways  and  all  the  time  parting  with  it.  So  long 
as  it  gains  more  than  it  loses  the  temperature  rises ;  when 
it  loses  more  than  it  gains  the  temperature  falls.  On  ordi- 
nary days  the  temperature  begins  to  rise  just  after  sunrise, 
and  rises  most  rapidly  in  the  middle  of  the  forenoon.  It 
stands  highest  at  about  two  or  three  o'clock,  and  then  falls 
through  the  remainder  of  the  day  and  all  the  night. 

Hang  a  thermometer  in  some  convenient  place  out  of 


Fig.  165.— The  influence  of  a  slanting  beam  is 
spread  over  a  larger  area  than  that  of  a  verti- 
cal beam. 


242    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


doors,  where  it  will  be  in  shadow  all  the  time,  and  then 
take  a  reading  every  hour.  Kule  a  sheet  of  paper,  as  in 
Fig.  166,  with  two  sets  of  lines.  Make  each  vertical  line 
stand  for  a  particular  hour  and  each  horizontal  line  for  a 
particular  degree  of  temperature,  and  mark  them  with 
figures  at  top  and  side.  Suppose  your  first  reading  in  the 
morning  is  at  six  o'clock  and  you  find  the  temperature  to 
be  24°.  Make  a  dot  on  the  paper  where  the  line  for  6 
A.  M.  is  crossed  by  the  line  for  24°.  At  seven  o'clock  you 
may  find  the  temperature  23°,  and  at  eight  o'clock  26°. 
Make  the  dots  at  the  proper  places,  and  connect  each  dot 
with  the  next  one  by  a  line.  At  the  end  of  the  day  you  will 
have  a  record  of  the  temperature.  In  the  figure  the  record  is 
complete  for  twenty-four  hours.     Such  a  record,  by  means 


.MIDNIGHT 
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NOON 
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P.M.  MIDNIGHT 

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40' 


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Fig.  166.— a  thermometer  record  for  a  complete  day,  beginning  at  6  A.  m. 

of  a  rising  and  falling  line,  is  called  a  Curve  of  Tempera- 
ture. The  upward  swing  in  the  afternoon  shows  the  warm- 
est part  of  the  day;  the  downward  swing,  near  morning, 


THE  ATMOSPHERE 


243 


POLAR 


shows  the  coldest  part  of  the  night.  Not  all  days  yield 
the  same  kind  of  record.  Clouds  may  interfere  with  the 
warming  of  the  air  or  with  its  cooling,  or  winds  may  bring 
warmer  or  cooler  air  from  some  other  place. 

212.  Temperature  and  latitude. — Let  us  think  of  the 
earth  at  one  of  the  equinoxes  (page  25),  when  day  and 
night  are  equal  in  all  the  zones,  for  these  positions  repre- 
sent the  average  for  the  whole  year.  In  tropical  lati- 
tudes (Fig.  167)  the  midday  rays  come  directly  down 
through  the  air  and  have  their 
greatest  heating  power ;  in  tem- 
perate regions  they  come  slant- 
ing to  the  ground  and  are  less 
effective;  and  in  polar  regions 
their  direction  is  still  less  favor- 
able. So  tropical  lands  and 
seas  are  very  warm,  polar  re- 
gions are  very  cold,  and  there 
is  a  gradual  transition  from 
tropical  warmth  to  polar  cold. 

It  is  true  that  in  another  part  of  the  year  the  northern 
hemisphere,  for  example,  is  tipped  toward  the  sun  and  gets 
more  heat;  but  this  advantage  is  exactly  balanced  by  a 
disadvantage  six  months  later.  The  tipping  causes  the 
yearly  procession  of  the  seasons,  but  does  not  affect  the 
average  or,  as  it  is  called,  mean  temperature. 

The  cause  of  the  seasons  has  been  so  fully  described  in 
Sections  19  to  22  that  only  a  reference  is  needed  in  this 
place,  but  mention  may  be  made  of  an  additional  fact 
which  Section  211  enables  us  to  understand.  Just  as  the 
day  heat  accumulates  till  the  middle  of  the  afternoon, 
so  the  summer  heat  accumulates  until  a  month  or  more 
after  the  solstice.  The  longest  days  come  in  the  second 
half  of  June,  and  the  sun's  rays  are  then  most  powerful, 
but  our  hottest  month  is  usually  July  or  August  instead 
of  June. 


POLAR 


Fig.  167.— Eelation  of  the  great  zones 
of  the  earth  to  the  sun's  rays  in 
March  and  September. 


244    AN  INTRODUCTION  TO   PHYSICAL   GEOGRAPHY 


The  normal  or  average  curves  of  temperature  for  the  year 
at  three  cities  are  given  in  Fig.  168.  The  curve  showing 
the  observations  for  a  single  year  would  not  be  smooth,  but 
very  irregular,  going  up  and  down  steeply  for  each  day  and 


JAN. 

FEB. 

MAR. 

APR. 

MAY 

JUNE  JULY 

AUG. 

SEPT. 

OCT. 

NOV. 

DEC. 

__ 



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NEW  ORLEANS 


5  CINCINNATI 


MONTREAL 


Fig.  168. — Annual  curves  of  temperature  for  New  Orleans  (lat.  30"),  Cincinnati  (lat. 
39°),  and  Montreal  (lat.  45°  30'). 

night,  and  for  all  the  warm  and  cold  periods.  Note  the 
differences  due  to  latitude,  also  that  Xew  Orleans  shows 
least  change  from  winter  to  summer.  This  is  because  it  is 
nearest  the  equator,  and  because  the  neighboring  waters  of 
the  Grulf  temper  the  climate  (Sec.  214). 

213.  Temperature  affected  by  winds  and  currents. — We 
have  seen  that  the  day  and  night  changes  of  tempera- 
ture are  not  always  the  same.  Nor  does  latitude  tell  us 
surely  the  amount  of  heat  which  the  air  will  contain  at  a 
given  place.  Great  winds,  either  steady  or  in  transient 
storms,  sweep  volumes  of  warm  air  into  cold  regions,  or 
masses  of  cold  air  into  warmer  places,  and  thus  cause 
great  and  often  sudden  variations,  as  when  a  warm  in- 
terval in  winter  or  summer  is  followed  by  a  sudden  drop 
of  20°,  30°,  or  40°  in  the  temperature.  Such  changes  will 
be  explained  in  the  following  chapter.  Ocean  currents 
also,  like   the   Gulf   Stream,  transfer  great  quantities  of 


THE  ATMOSPHERE  245 

warm  or  cold  water  across  thousands  of  miles  of  latitude, 
and  change  thus  the  amount  of  heat  in  the  overlying  air. 

214.  Temperature  aflfected  by  land  and  water. — Earth  and 
rock  are  not  penetrated  by  the  sun's  rays.  The  daily  warm- 
ing and  nightly  cooling  extend  but  a  few  inches  into  the 
ground.  Even  the  accumulated  heat  of  summer  does  not 
penetrate  many  feet.  But  water  allows  the  rays  to  enter 
freely  to  some  scores  or  hundreds  of  feet  in  depth,  and 
through  all  this  space  receives  heat.  The  sea  warms  less 
rapidly  than  the  land,  but  when  warmed  retains  heat  longer. 
Hence  the  temperatures  are  less  extreme  and  less  exposed 
to  sudden  change  on  water  than  on  land.  The  winter 
voyager  on  the  ocean  often  encounters  but  a  moderate  de- 
gree of  cold.  Thus  we  can  understand  why  the  climate  is 
more  mild  in  the  autumn  in  the  presence  of  large  lakes. 
Frosts  hold  off  so  long  as  the  body  of  warm  water  is  giving 
forth  the  heat  accumulated  in  the  summer.  This  is  one 
of  the  reasons  why  the  lake  regions  of  western  New  York 
have  proved  favorable  for  the  raising  of  fruits.  But  as  the 
cold  becomes  intense,  the  surface  waters  are  chilled,  grow 
dense,  and  sink  to  the  bottom,  until  at  length  the  waters 
as  a  whole  have  lost  much  heat,  and  the  smaller  or  more 
shallow  lakes  are  frozen  over. 

215.  Temperature  affected  by  altitude. — Illustrations  of 
increasing  cold  and  changing  plant  growth  have  already 
been  given  in  our  study  of  mountains  (Sec.  177).  As  a 
rule  the  temperature  decreases  about  1°  for  every  300  feet 
of  altitude.  Two  experiments  will  help  to  explain  this.  Fill 
a  bicycle  tire  by  means  of  an  ordinary  bicycle  pump.  Then 
feel  the  pump  cylinder  and  tire.  The  cylinder  is  warm, 
especially  at  the  end  where  the  air  has  been  compressed, 
and  the  tire  is  also  warm.  This  means  that  the  air  has 
been  warmed  by  compression.  Wait  until  the  tire  has 
cooled  to  the  temperature  of  the  surrounding  air ;  then 
open  the  valve  and  let  the  air  in  the  tire  escape.  As  it 
blows  on  your  hand  you  feel  that  it  is  cold.     It  has  been 


246    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

cooled  by  expansion.  The  general  principle  is  that  air  and 
other  gases  grow  warm  when  they  are  crowded  into  less 
space,  and  grow  cool  when  they  push  apart  so  as  to  occupy 
more  space. 

As  we  shall  presently  see,  the  air  has  many  motions. 
Some  of  them  are  horizontal,  others  up  and  down.  When  a 
body  of  air  goes  down,  it  is  subject  to  more  pressure  (Sec. 
198),  and  the  compression  warms  it ;  when  air  goes  up  it  is 
partly  relieved  of  pressure,  and  its  expansion  cools  it.  Thus 
the  changes,  back  and  forth,  between  higher  and  lower 
parts  of  the  atmosphere  keep  the  lowlands  warmer  than 
the  uplands  and  give  to  the  loftiest  peaks  perpetual  frost. 

216.  The  mapping  of  temperature.  Isotherms. — We  shall 
see,  as  we  go  on,  that  it  is  important  to  record  the  tem- 
perature of  many  places  on  a  map,  so  that  the  distribution 
of  heat  over  large  regions  may  be  seen  at  a  glance.  This 
is  accomplished  by  having  reports  of  thermometer  readings 
at  a  given  time  sent  in  by  telegraph  from  hundreds  of  ob- 
servers in  different  places.  These  temperature  figures  are 
written  on  the  map  in  their  proper  places.  Lines  are  now 
drawn  through  places  having  equal  temperatures.  This 
will  be  best  understood  by  studying  a  temperature  map 
of  the  United  States  (Fig.  169).  The  one  chosen  is  for 
January  7,  1886,  at  7  a.  m.  A  dotted  line  has  been  traced 
through  all  stations  reporting  a  temperature  of  zero.  We 
find  the  line  running  from  Quebec  past  Buffalo.  Then  it 
swings  far  to  the  north  and  almost  follows  the  curve  of  the 
north  shore  of  Lake  Superior.  It  then  passes  south  and  west 
through  Minnesota,  Iowa,  eastern  Nebraska,  and  Kansas, 
crosses  southern  Colorado,  and  runs  up  to  northwestern 
Utah.  The  map  does  not  mean  that  the  belt  of  zero  tem- 
perature stopped  at  Montreal  and  in  Nevada,  but  only  that 
observations  were  not  reported  beyond  those  two  points. 
All  areas  north  of  this  line  have  temperatures  below  zero, 
and  the  lines  are  drawn  for  each  10  degrees  down  to 
—30°.     This   is  in  Montana.     There  were  doubtless  still 


THE  ATMOSPHERE  247 

lower  temperatures  farther  north,  but  the  curves  beyond 
the  United  States  boundary  are  not  given.  In  the  east  the 
line  for  —10°  is  a  little  north  of  Lake  Ontario.  Thus  it 
appears  that  intense  cold  prevailed  in  Canada,  extending 
down  into  New  York  at  the  east,  and  as  far  down  as  the 
southern  border  of  Colorado  in  the  west. 

All  the  land  south  of  the  zero  line  was  warmer.  Thus 
we  find  20°  at  Cincinnati,  30°  near  Little  Eock,  40°  south 
of  Vicksburg,  and  50°  at  Galveston.  The  line  of  32° — that 
is,  of  the  freezing  temperature — is  not  drawn,  but  would 
run  a  little  south  of  the  line  for  30°.  This  suggests  that  a 
line  might  be  drawn  for  every  degree,  if  observations  were 
numerous  enough,  but  so  many  lines  would  make  a  con- 
fused map.  Such  lines  are  called  Isotherms  (meaning 
equal  heat),  and  they  are  an  essential  part  of  all  weather 
maps. 

This  map  should  be  studied  thoroughly,  for  it  explains 
the  principle  of  all  temperature  maps ;  but  it  shows  the 
conditions  for  one  morning  only  in  one  country.  With  ob- 
servations enough,  and  if  it  were  possible  to  have  reported 
them  from  all  lands  and  all  parts  of  the  sea,  a  temperature 
chart  of  the  world  for  that  morning  could  have  been 
made.  This  can  not  be  done,  but  records  can  be  kept  by 
thousands  of  observers  in  different  countries  and  on  board 
ship  in  all  oceans,  and  a  map  of  mean  temperatures  for  a 
longer  time  can  be  made.  For  example,  if  the  thermometer 
were  read  several  times  each  day  and  night  for  a  month 
in  New  York  city,  we  could  easily  find  the  mean  tempera- 
ture for  that  month.  Doing  the  same  for  all  weather 
stations  in  the  United  States,  and  putting  the  means  on 
the  map,  as  we  did  the  records  of"  one  cold  morning,  we 
could  draw  the  isotherms  for  the  month. 

The  student  will  now  be  ready  to  study  three  maps 
showing  mean  temperatures  for  the  world.  Fig.  170  shows 
the  isotherms  for  January.  This  means  that  all  possible 
observations  on  land  and  sea  have  been  taken  into  account, 


248 


250    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

averaged  for  each  locality,  and  the  lines  drawn  through 
points  of  equal  mean  temperature.  Fig.  171  shows  the 
same  for  July,  and  Fig.  172  for  the  entire  year.  It  will 
not  be  possible  to  point  out  all  that  may  be  learned  from  a 
study  of  these  charts,  but  some  of  the  more  important  facts 
are  as  follows  : 

(1)  The  isotherms  run  in  general  east  and  west  direc- 
tions around  the  globe,  like  parallels  of  latitude,  but  in 
curved  instead  of  straight  lines. 

(2)  Sometimes  the  curves  are  strong,  showing  that  dif- 
ferences of  land  and  water  change  the  amount  of  heat  that 
would  otherwise  be  present.  Thus  the  January  isotherms 
run  far  north  in  the  Atlantic. 

(3)  The  isotherms  are  more  regular  in  the  southern 
hemisphere,  because  there  the  almost  continuous  water 
gives  a  more  even  temperature. 

(4)  In  passing  from  north  to  south,  in  any  longitude, 
the  temperatures  met  are  first  higher  and  higher,  and  then 
lower  and  lower ;  at  some  point  a  highest  temperature  is 
passed.  The  line  connecting  all  such  points  is  called  the 
Heat  Equator.  It  is  a  curved  line  and  does  not  closely  fol- 
low the  geographic  equator. 

(5)  In  January  all  the  isotherms  in  both  hemispheres, 
and  the  heat  equator  also,  are  farther  south  than  in  July. 
The  lines  sway  to  and  fro  with  the  sun. 

One  thing  which  the  maps  do  not  show  is  the  variation 
of  temperature  according  to  height.  Whenever  the  record 
gave  the  readings  on  a  mountain  or  plateau,  a  certain 
amount  was  added  so  as  to  obtain  the  corresponding  temper- 
ature at  the  level  of  the  sea,  and  the  sea-level  temperature 
was  used  in  making  the  map. 

Further  illustrations  of  the  distribution  of  heat  in  vari- 
ous parts  of  the  world  will  be  given  in  the  chapter  that 
follows. 

217.  The  Mercator  projection. — Each  of  our  maps  of  iso- 
therms shows  nearly  the  whole  of  the  earth's  surface,  but 


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251 


252    AN  INTRODUCTION  TO   PHYSICAL  GEOGRAPHY 

is  square-cornered  instead  of  being  round  like  the  maps  in 
Fig.  6.  Let  us  interrupt  the  study  of  the  air  for  a  moment 
to  see  if  we  can  understand  why  maps  of  the  same  thing  do 
not  always  have  the  same  shape.  The  skin  of  an  orange, 
or  any  large  piece  of  it,  can  not  be  made  to  lie  out  flat 
without  stretching  some  parts.  For  the  same  reason  a 
map  of  the  round  earth  can  not  be  drawn  on  flat  paper 
without  giving  some  parts  the  wrong  size  or  wrong  shape. 
In  trying  to  make  this  unavoidable  error  as  small  as  pos- 
sible, geographers  have  contrived  several  different  ways  of 
drawing  maps,  each  one  being  best  for  some  particular  use. 
The  arrangements  are  called  Projections  and  have  separate 
names.  The  maps  in  Figs.  170,  171,  and  172  are  drawn  on 
the  Mercator  projection.  Imagine  the  surface  of  the  earth 
to  be  divided  along  a  meridian  and  thus  unrolled  into  a 
sheet,  with  the  equator  in  the  middle  and  the  polar  parts 
at  the  edges.  All  except  a  belt  near  the  equator  must  of 
course  be  stretched,  the  amount  of  stretching  being  greater 
at  a  distance  from  the  equator  than  near  it.  Thus,  in  Fig. 
172  the  parallel  of  80°  is  as  long  as  the  equator,  although 
on  a  globe  it  is  less  than  one-fifth  as  long ;  and  Greenland 
seems  larger  than  Australia,  though  really  much  smaller. 
This  projection  is  useful  when  we  wish  to  bring  all  sides 
of  the  earth,  except  the  poles,  into  one  view. 


CHAPTEE   XI 

WINDS,   STORMS,   AND    CLIMATE 

This  chapter  will  deal  especially  with  the  movements 
of  the  atmosphere.  We  have  seen  how  the  air  is  made 
up,  and  have  studied  some  of  its  relations  to  moisture, 
light,  and  heat,  but  before  we  can  understand  its  move- 
ments we  must  know  it  in  another  way — as  regards  its 
pressure. 

218.  Pressure  of  the  atmosphere. — We  have  already  seen, 
in  Section  198,  that  the  atmosphere  presses  downward,  and 
that  its  pressure  is  greater  at  low  levels  than  at  high. 
This  pressure  depends  on  the  weight  of  the  air,  and  varies 
somewhat  in  amount  at  any  place  as  the  temperature  or 
moisture  of  the  air  is  changed.  The  ordinary  or  mean 
pressure  is  called  the  normal  pressure.  The  normal  pres- 
sure at  the  level  of  the  sea  is  about  15  pounds  on  each 
square  inch  of  surface. 

We  can  tell  in  a  rough  way  how  warm  or  cold  it  is  by 
our  sensations,  but  we  know  nothing  thus  of  the  amount 
of  pressure  which  the  air  exerts  in  its  different  conditions, 
except,  as  has  been  said,  at  great  heights.  We  measure 
the  pressure  by  means  of  instruments  called  Barometers 
(from  words  meaning  weight  and  measure).  One  kind  of 
barometer  is  made  with  mercury  and  a  glass  tube.  The 
glass  tube,  which  must  be  nearly  a  yard  long  and  closed  at 
one  end  {B  in  Fig.  173),  is  filled  with  mercury,  and  then 
inverted  with  the  open  end  in  a  basin  of  mercury,  care 
being  taken  to  admit  no  air  in  the  tube.  The  mercury 
does  not  all  run  down  into  the  basin,  but  only  part  of  it ; 

253 


254     AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


'« 


n 


the  rest  stands  in  the  tube,  with  an  empty  space  {n  to  B) 
above  it.  You  will  understand  why  this  is  so  if  you  con- 
sider that  the  atmosphere  presses  orT  the  mercury  in  the 
basin,  but  there  is  nothing  to  press  on  the  mercury  in  the 
tube.  The  mercury  stands  just  high  enough  in  the  tube 
for  its  weight  to  balance  the  pressure  of 
the  air  on  the  outside  mercury.  If  the 
air  pressure  increases  or  diminishes,  the 
column  of  mercury  grows  longer  or 
shorter,  and  its  length  therefore  meas- 
ures the  pressure.  At  sea-level  the  nor- 
mal height  of  the  mercury  column  in 
the  barometer  is  30  inches.  For  brevity 
we  commonly  say  that  the  pressure  of 
the  air  at  sea-level  is  30  inches. 

If  we  carry  the  instrument  up  a 
mountainside  the  top  of  the  column  will 
settle  about  one  inch  for  each  900  feet 
of  ascent.  Hence  it  is  that  the  barom- 
eter can  be  used  for  ascertaining  alti- 
tude, when  carried  in  a  short  time  from 
one  point  to  a  higher  position.  As  the 
mercurial  barometer  is  heavy  and  incon- 
veniently carried,  another  instrument, 
called  the  aneroid  barometer,  is  more 
often  used  for  this  purpose. 

219.  Maps  showing  atmospheric  pres- 
sures.    Isobars. — As  in  the  case  of  tem- 
perature, so  with  pressiire,  it  is  impor- 
being  at  the  level  of   taut  to  know  the  Condition  not  only  at 

the    mercury    surface    ^^g  ^q:^^^  ^^^  ^^  ^  j^  jg  convenient 

outside  the  tube.  ^  *' 

to  record  the  figures  for  pressure  at 
the  respective  points  on  a  map,  as  of  the  United  States. 
The  same  persons  who  observe  temperatures  read  their 
barometers  for  pressure,  and  in  the  Weather  Service  trans- 
mit the  reading  to  Washington.     We  shall  best  understand 


Fig.  173.— The  barometer 
tube  and  mercury.  In 
the  complete  instru- 
ment a  scale  of  inches 
stands  beside  the  tube, 
the  zero  of  the  scale 


WINDS,   STORMS,   AND  CLIMATE  255 

by  taking  a  real  case,  and  will  choose,  as  before,  January  7, 
1886,  at  7  A.  M.  The  atmospheric  pressures  for  all  stations 
then  reporting  in  the  United  States  were  first  put  down  on 
a  map.  Then  lines  were  drawn  through  all  points  haying 
the  same  pressure.  In  the  case  of  pressure,  one-tenth  of  an 
inch  is  an  important  variation,  and  the  map  was  arranged 
to  show  differences  of  this  amount.  These  lines,  called 
Isobars,  are  shown  in  Fig.  174,  and  the  isotherms  of  Fig. 
169  are  also  given.  Let  the  student  observe  that  there  is  a 
belt  of  normal  pressure,  marked  by  the  isobar  of  30  inches, 
running  from  New  York  southward  to  the  Carolinas. 
Other  isobars,  for  29.9,  29.8,  etc.,  appear  to  the  eastward 
or  to  the  northeast  until  in  Nova  Scotia  we  find  29.2,  and 
the  region  is  marked  as  having  Low  pressure. 

To  the  west  of  the  isobar  of  30  inches  we  see  that  the 
lines  swing  around  to  the  west  and  run  across  the  continent, 
with  higher  and  higher  pressures  in  the  northwest,  until 
the  last  isobar  curves  around  the  south  side  of  an  area 
marked  High,  in  Montana.  The  pressure  there  is  30.8 
inches.  Curving  across  the  southern  United  States  is  an- 
other isobar  for  30  inches,  and  south  of  that  the  pressure 
diminishes  until,  in  southern  Texas  and  Mexico,  we  find 
another  area  marked  low,  but  still  0.6  of  an  inch  higher  than 
the  low  area  of  Nova  Scotia. 

Thus  we  find,  on  the  morning  of  January  7,  1886,  one 
area  of  high  pressure  and  two  of  low  pressure,  all  on  the 
edge  of  the  United  States,  or  just  beyond.  In  the  inter- 
mediate regions  the  pressure  is  also  intermediate.  The 
most  important  contrast  is  between  the  northeast  and  the 
northwest,  ranging  from  29.2  up  to  30.8  inches. 

All  these  pressures  are  supposed  to  be  measured  at  sea- 
level.  In  the  interior  of  the  continent  the  barometers  used 
are  actually  several  thousand  feet  above  sea-level,  but  an 
allowance  has  been  made  in  each  case  for  the  loss  of  pres- 
sure due  to  height,  and  the  pressure  marked  on  the  map  is 
that  which  would  have  been  found  if  the  barometer  had 
18 


256    AN  INTRODUCTION  TO   PHYSICAL   GEOGRAPHY 

been  carried  down  a  deep  well  to  the  level  of  the  sea  and 
there  read. 

The  condition  of  the  air  continually  changes,  and  the 
map  we  have  just  studied  represents  the  temperatures  and 
pressures  only  for  a  single  part  of  one  day.  This  will  be 
plain  if  we  now  look  at  a  map  for  twenty-four  hours  later, 
7  A.  M.,  January  8,  1886  (Fig.  175).  The  student  must  re- 
member that  continuous  lines  represent  the  belts  of  equal 
pressure,  and  for  the  present  should  neglect  the  other  sym- 
bols of  the  map.  The  high-pressure  area  has  moved  east- 
ward and  is  more  in  Xorth  Dakota  than  in  Montana,  and 
the  figure  is  30.9  instead  of  30.8.  The  isobars  nearly  enclose 
it  instead  of  curving  broadly  south  of  it.  Pressure  is  still 
low  in  Nova  Scotia  but  has  slightly  increased,  being  29.7 
instead  of  29.6.  The  greatest  change  is  seen  in  the  south, 
where  a  well-developed  center  of  low  pressure  appears  on 
the  Gulf  coast,  the  lowest  isobar  marking  29.5. 

Again,  let  us  study  the  pressures  one  day  later,  January 
9  (Fig.  176).  The  high-pressure  area  has  slowly  moved 
eastward  and  is  in  central  North  Dakota.  A  subordinate 
center  of  high,  but  not  very  high,  pressure  (30.3)  has  devel- 
oped in  Utah,  Nevada,  and  Idaho.  The  great  Gulf  center 
of  low  pressure  has  moved  far  up  to  the  northeast,  being 
central  in  New  Jersey,  with  a  pressure  of  only  28.7.  Vary- 
ing pressure  in  any  one  place,  and  a  moving  to  and  fro  of 
centers  and  belts  of  high  and  low  pressure — these  are  the 
principles  emphasized  at  this  point.  The  student  should 
ask  himself  whether  he  now  clearly  knows  the  meaning  of 
isotherms  and  isobars,  and  thus  can  read  a  map  showing 
atmospheric  temperatures  and  pressures.  If  he  can  do  this 
he  is  prepared  for  a  further  step. 

220.  Winds. — Let  us  turn  again  to  our  series  of  maps, 
taking  first  Fig.  174.  The  arrows  show  the  direction  toward 
which  the  wind  blows,  as  reported  by  different  observers  on 
the  morning  of  January  7.  In  the  east  they  point  toward 
the  center  of  low  pressure.     In  the  west  they  are  more 


WINDS,   STORMS,   AND  CLIMATE 


257 


scattering  because  reports  are  fewer,  but  they  are  pointing 
away  from  the  centers  of  high  pressure.  This  is  a  general 
law,  that  winds  blow  from  regions  of  greater  pressure  to 
those  of  less.  If  a  fire  be  built  in  a  stove  which  stands 
in  a  large  cold  room,  the  region  around  and  above  the 
stove  is  warmed,  and  its  air  becomes  less  dense ;  it  there- 
fore is  a  region  of  low  pressure,  and  the  colder,  heavier  air 
from  the  sides  crowds  in  and  displaces  the  warm  air,  which 
is  thus  forced  upward.  The  draft  toward  the  stove,  whether 
strong  enough  to  be  felt  or  not,  illustrates  the  origin  of 
winds.  They  are  sidewise  movements  by  which  the  heavier 
air  from  centers  or  regions  of  high  pressure  is  rushing  toward 
the  regions  of  low  pressure.  There  are  always  winds  blow- 
ing somewhere,  and  winds  blow  at  frequent  intervals  every- 
where, because  something  is 
always  taking  place  to  cause 
unequal  pressure.  Heat 
comes  into  and  goes  out  from 
the  air,  through  the  succes- 
sion of  day  and  night,  by  the 
changes  of  seasons,  and  in  re- 
gions of  varying  height  and 
varying  moisture.  The  at- 
mosphere is  a  sea  of  gas,  now 
at  rest,  now  in  gentle  motion, 
and  now  tumultuous  like  the 
ocean  in  a  storm. 

One  further  statement 
should  be  made  about  this 
general  principle  of  wind 
formation.  If  the  centers  of 
high  and  low  pressure  are 
comparatively  close  together, 

the  rush  from  one  to  the  other  is  powerful  and  the  wind 
has  high  velocity.  In  such  case  the  isobars  lie  close  to- 
gether.    The  technical  way  of  putting  it  is  that  the  pres- 


FiG.  177.— The  anemometer.  Inside  the 
upright  is  a  spindle  to  which  the 
cross-bars  are  fastened.  The  wind 
pushes  harder  against  the  hollows  of 
the  cups  than  against  the  outsides, 
and  thus  turns  the  spindle.  The 
stronger  the  wind,  the  faster  the  spin- 
dle whirls.  A  counting  machine  be- 
low is  worked  by  the  spindle  and 
makes  a  record. 


258    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

sure  slope  or  Gradient  is  steep.  The  velocity  of  winds  is 
stated  in  miles  per  hour.  Under  10  miles  we  may  call  a 
wind  a  breeze.  A  strong  wind  has  a  rate  of  20  to  30  miles, 
40  to  50  miles  marks  a  gale,  and  a  hurricane  has  still 
higher  speed.  The  direction  of  the  wind  is  determined, 
if  accuracy  is  desired,  by  a  Wind  Vane,  and  the  velocity 
is  measured  by  an  instrument  known  as  an  Anemometer 
(Fig.  177). 

221.  Prevailing  westerly  winds. — In  the  middle  latitudes 
of  both  northern  and  southern  hemispheres,  the  winds  more 
often  come  from  the  west  than  from  any  other  direction. 
This  is  true  to  some  extent  even  farther  north  and  south. 
These  winds  are  often  briefly  mentioned  as  the  Prevailing 
Westerlies.  We  do  not  now  ask  why  more  winds  should 
come  from  the  west,  but  observe  that  we  have  here  one  of 
the  great  parts  of  the  atmospheric  circulation  of  the  planet. 
These  winds  blow  more  steadily  in  the  southern  hemisphere 
than  in  ours,  because  there  is  less  interruption  by  lands. 
Sailing  vessels  readily  go  by  the  way  of  Cape  of  Good  Hope, 
cross  the  South  Pacific,  and  return  by  Cape  Horn,  while  it 
is  difficult,  especially  near  Cape  Horn,  to  make  the  voyage 
in  the  opposite  direction. 

222.  Storms  of  the  westerly  winds,  or  cyclones.— These 
winds,  especially  in  the  northern  middle  zone,  do  not  blow 
forever  to  the  east  without  interruption.  They  break  into 
vast  whirls  or  spirals,  something  like  a  small  whirlwind, 
excepting  that  the  winds  are  not  always  swift,  and  the  whirl 
may  be  several  hundred  or  one  thousand  miles  across.  Fig. 
178  shows  such  a  whirl  in  the  eastern  United  States.  The 
winds  are  blowing  toward  the  center,  not  directly,  but 
in  a  spiral  way,  and  swinging  around  from  right  to  left. 
As  we  may  know  from  the  inflow  of  the  winds,  this  is  a 
low-pressure  area.  It  is  partly  a  region  of  rain,  as  indi- 
cated by  the  shading.  Low  pressure,  relatively  high  tem- 
perature, rain,  and  shifting  winds  characterize  the  region. 
It  is  a  Cyclone  or  Cyclonic  Storm.     This  is  the  proper  use 


WINDS,   STOEMS,    AND  CLIMATE  259 

of  the  word  cyclone,  and  we  should  not  apply  it  to  the 
tornado. 

Now  this  cyclonic  whirl  is  not  stationary  but  moving, 
usually  in  an  eastward  or  northeastward  direction.  It  will 
be  followed  by  a  center  or  area  of  high  pressure,  also 
steadily  moving  eastward.  In  this  case  the  winds  flow 
spirally,  but  out  from  the  center.  Such  a  whirl  is  called 
an  Anticyclone.  It  is  associated  with  low  temperature  and 
clear  skies.  As  the  cyclone  with  its  variable  and  warmer 
winds  passes,  the  skies  clear,  the  winds  come  from  the 
northwest,  the  anticyclonic  whirl  takes  possession,  and  we 
say  that  a  cold  wave  has  come.  We  may  again  refer  to  Fig. 
176.  Observe  the  center  of  low  pressure  on  the  Atlantic 
coast,  the  inflowing  winds,  the  temperature  of  about  20°, 
and  the  great  area  of  rain  and  snow  stretching  westward 
beyond  the  Mississippi.  The  chief  high-pressure  area  is  on 
the  Canadian  border,  the  sky  is  clear,  the  winds  flow  out, 
and  the  temperature  is  —50°.  Thus  the  low  and  high  areas 
follow  each  other  across  our  continent.  We  may  now  un- 
derstand why  the  temperature  sometimes  falls  suddenly, 
30°  or  40°  or  even  50°.  It  happens  in  the  rear  of  a  cyclonic 
storm.  We  shall  have  occasion  to  review  these  important 
facts  in  the  section  on  weather  prediction. 

223.  Trade-winds. — These  are  the  most  important  move- 
ments of  the  atmosphere  in  the  tropical  and  equatorial  re- 
gions. They  prevail  in  general  to  28°  north  and  south 
latitude.  They  blow  obliquely  toward  the  equator  from 
the  northeast  and  southeast.  Thus  there  is  a  broad  belt  of 
northeast  trades  in  the  northern  hemisphere  and  a  similar 
belt  of  southeast  trades  south  of  the  equator.  Their  veloc- 
ity is  10  to  30  miles  per  hour.  They  have  received  their 
name  from  the  steadiness  with  which  they  flow.  The  trade- 
wind  belt  is  usually  clear,  notwithstanding  the  winds  blow 
over  warm  seas.  The  reason  is  that  the  air  is  moving  from 
cooler  to  warmer  regions  and  thus  can  hold  more  vapor 
without  forming  clouds.     Between  the  northern  and  south- 


260    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

ern  trades  is  a  belt  of  calms.  Here  the  moist,  warm  air  of 
the  trades  rises  to  greater  heights,  is  chilled  and  sends 
down,  almost  daily,  abundant  rains.  This  region  is  called 
the  Doldrums.  The  Atlantic  trades  give  up  great  quanti- 
ties of  moisture  in  equatorial  South  America,  and  up  the 
eastern  slope  of  the  Andes.  The  west  side  of  the  range, 
however,  as  in  Peru,  is  dry.  Thus  we  see  here  the  reverse 
of  the  conditions  caused  by  the  prevailing  westerlies  and 
the  mountains  of  our  Pacific  coast. 

Outside  of  the  trade-wind  belts  in  both  hemispheres  is 
a  belt  of  calms  and  light  winds,  in  which,  however,  the  cur- 
rents of  air  are  descending.     These  regions  are  called  the 


Pig.  179.— Paths  usually  followed  by  centers  of  cyclonic  storms  across  the  United 
States.  Path  B  brings  more  storms  than  any  other  to  the  main  track,  A.  Storms 
from  the  southwest  (D,  E)  are  comparatively  mild.  Tropical  hurricanes  follow 
path  F. 

Horse  Latitudes.  Thus  we  have  a  great  series  of  parallel 
wind  belts.  It  is  important  to  observe  that  the  entire  sys- 
tem of  tropical  and  equatorial  belts  shifts  somewhat  north- 
ward and  southward  with  the  sun  in  the  annual  change  of 
of  seasons.     More  will  be  said  of  them  in  Section  230. 


Fig.  180.— Winds  of  the  Atlantic  Ocean.    The  long  arrows  show  directions   of  steady- 
winds,  the  short  arrows  the  prevailing  directions  of  variable  winds. 

261 


262    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

224.  Monsoons. — We  shall  define  these  winds  by  a  de- 
scription of  the  best  illustration  of  them.  They  blow  over 
southern  Asia  and  the  Indian  Ocean.  In  the  summer  all 
the  lands  of  India  and  central  Asia  become  much  heated. 
The  expansion  of  the  air  makes  its  weight  and  pressure  less 
than  over  the  Indian  Ocean.  High  pressure  over  the  ocean 
and  low  pressure  over  the  land  cause  winds  toward  the  land, 
and  they  blow  strongly  and  steadily  all  through  the  summer 
months  (Fig.  182).  The  southeast  trades  swing  around 
near  the  equator  and  blow  from  the  southwest  over  southern 
Asia.  To  these  winds  are  due  the  excessive  rains  and  wet 
season  of  southern  India.  In  the  northern  winter,  on  the 
other  hand,  the  heat  equator  shifts  southward,  the  Asiatic 
lands  are  chilled,  the  air  is  cold  and  heavy,  and  the  pressure 
is  greater  than  above  the  ocean.  Hence  there  is  a  rush 
from  the  land  to  the  sea.  The  northeast  trades  now  swing 
across  the  equator  into  the  southern  hemisphere  (Fig.  181), 
and  India  has  its  dry  season.  These  great  periodical  or 
seasonal  winds  are  the  Monsoons.  The  arrangement  of 
land  and  sea  favors  their  development  in  this  region.  Sim- 
ilar winds  occur  in  the  Gulf  and  lower  Mississippi  Valley, 
but  they  are  less  developed,  and  are  not  commonly  called 
monsoons,  this  being  an  Oriental  word. 

225.  Land  and  sea  breezes. — These  are  not  to  be  con- 
fused with  monsoons,  though  they  are  like  them  in  flowing 
now  from  the  land  and  now  from  the  water.  They  are 
light  winds  which  spring  up  by  day  and  night.  As  the 
land  heats  and  cools  more  quickly  than  the  sea,  it  often 
becomes  warmer  than  the  adjacent  water  during  the  day 
and  cooler  at  night,  and  it  communicates  its  temperature 
to  the  lower  part  of  the  air.  So  by  day  the  air  above  the 
sea  is  the  heavier  and  flows  toward  the  land,  and  at  night 
the  cool  air  above  the  land  flows  toward  the  sea.  The 
same  changes  may  take  place  on  the  borders  of  lakes. 
These  are  daily  changing  breezes,  therefore,  while  mon- 
soons are  steady  winds  changing  with  the  seasons. 


FiQ.  181.— Winds  of  the  Indian  Ocean  in  January  and  February,    The  winds  north 
of  the  equator  are  the  Northeast  Monsoon,  or  Dry  Monsoon. 


Fig.  182. — Winds  of  the  Indian  Ocean  in  July  and  August.    The  winds  north  of  the 
equator  are  the  Southwest  Monsoon,  or  Wet  Monsoon.    See  page  262. 

263 


264    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

226.  Day  breezes  and  night  calms.— The  student  has 
often  noticed  that  considerable  breezes  may  rise  during  a 
warm  summer  day,  but  that  they  usually  subside  toward 
evening,  leaving  the  air  calm.  During  the  day  the  air 
near  the  ground  becomes  much  more  heated  than  the 
upper  air,  owing  to  its  receiving  much  heat  by  radiation 
from  the  earth.  Hence  the  heavier  air  above  sinks  through 
the  lighter  air  below  and  crowds  it  away  here  and  there, 
causing  sidewise  movements  or  breezes.  These  movements 
cease  when  the  sun's  warmth  is  withdrawn. 

227.  Thunder-storms. — We  have  as  yet  studied  but  one 
kind  of  disturbance  to  which  we  give  the  name  of  storm — 
namely,  the  Cyclone  or  broad  spiral  whirl,  developing  in 
connection  with  the  westerly  winds  in  middle  latitudes. 
We  now  take  up  special  kinds  of  storms,  which  are  alike 
in  that  most  of  them  are  somewhat  local  and  all  are  more 
or  less  sudden  and  violent.  We  take  first  the  Thunder- 
storm. 

The  student  is  familiar  with  the  common  character  of 
such  a  storm.  It  usually  occurs  in  warm  latitudes  or  in 
the  warm  season  of  the  temperate  regions.  It  often  fol- 
lows a  period  of  intense  heat  and  usually  occurs  in  the 
afternoon.  It  is  heralded  by  the  approach  of  large  cumulus 
clouds  from  the  west.  A  sharp  breeze  springs  up,  the  sky  is 
overspread,  and  rain  pours  down.  After  a  short  time,  usu- 
ally not  above  a  half-hour,  the  rain  ceases,  the  clouds  move 
to  the  eastward,  the  sun  shines,  and  a  rainbow  appears. 
The  rapidly  forming  cumulus  cloud  marks  a  swift  up-draft 
of  heated  air  which  expands  because  it  rises,  cools  because 
it  expands,  and  discharges  rain  because  it  cools.  The  light- 
ning is  due  to  the  electricity  generated  in  the  clouds  in 
their  sudden  formation.  It  is  an  electric  spark,  like  other 
electric  sparks  except  for  its  intensity  and  power.  The 
thunder  is  caused  by  sharp  vibrations  set  up  in  the  atmos- 
phere by  the  passage  of  electricity.  It  comes  to  us  later 
because  sound  travels  more  slowly  than  light ;  it  continues 


WINDS,   STORMS,   AND  CLIMATE 


to  roll  because  the  sound  from  remote  parts  of  the  flash  re- 
quires more  time  to  reach  us. 

In  the  temperate  latitudes  the  thunder-storm  is  usually 
associated  with  the  cyclonic  storm,  and  is  most  often  re- 
ported as  occurring  some  hundreds  of  miles  south,  south- 
east, or  southwest  of  the  cyclonic  center,  or  area  of  low 
pressure.  Many  thunder-storms  occur  near  the  equator, 
in  the  belt  of  calms,  where  the  warm  air  is  chilled  by  rising 
(Sec.  215).  These  take  a  westerly  direction.  Thus  trop- 
ical thunder-storms  follow  the  trade-winds,  and  middle- 
latitude  thunder-storms  follow  the  eastward  moving  cyclones 
of  the  westerly  winds. 

228.  Tornadoes. — These  are  violent,  whirling  disturb- 
ances, arising,  like  thunder-storms,  in  connection  with 
cyclones.  A  dark  fun- 
nel -  shaped  cloud  ex- 
tends down  to  the  earth 
with  a  swift,  whirling 
motion,  at  the  same 
time  rushing  swiftly 
over  the  land.  The 
wind  has  such  force  as 
to  destroy  houses,  up- 
root trees,  and  hurl  men 
and  animals  for  consid- 
erable distances  through 
the  air,  but  the  path  of 
destruction  is  narrow — 
only  a  few  hundred 
yards  wide.  Such  storms 
are  often  reported  as 
cyclones,  but  this  term  should  be  reserved  for  the  larger, 
less  violent  storms  already  described.  A  tornado  at  sea  is 
called  a  Waterspout. 

229.  Tropical  hurricanes.— These  are  also  called  tropical 
cyclones,  because,  like  the  cyclones  already  described,  they 


Fig.  183.— a  waterspout ;  Vineyard  Sound,  Au- 
gust 19,  1896.  From  a  photograph  ;  copy- 
righted by  Baldwin  Coolidge, 


266    AN  INTRODUCTION  TO   PHYSICAL   GEOGRAPHY 

are  whirling  storms.  The  whirls  are  not  so  extensive  as 
those  of  higher  latitudes,  but  they  may  still  have  a  diameter 
of  300  miles  or  more,  and  the  spirally  blowing  winds  are 
much  more  violent,  reaching  velocities  of  60  to  70  miles 
per  hour.  They  start  in  the  equatorial  belt  of  calms  and 
travel  westward.  Those  of  the  Atlantic  often  swing  around 
and  pass  northward  over  the  West  Indies  and  Gulf  region 
and  then  bear  to  the  northeast  off  the  eastern  shores  of  the 
United  States.  These  storms  do  not  form  on  the  land. 
Being  always  on  the  sea  and  of  exceeding  violence,  they 
are  most  dangerous  to  ships,  which  have  often  been  greatly 
injured  or  wrecked  by  them.  The  spiral  movement  does 
not  extend  to  the  center.  There  an  area  of  calm  is  found 
10  to  20  miles  across,  which  is  called  the  eye  of  the  storm. 
Within  it  the  sky  is  clear.  Outside,  but  not  far  from  this 
central  area,  the  clouds  are  dense,  often  causing  darkness, 
and  heavy  rains  fall.  The  progress  of  such  a  storm  occu- 
pies several  days,  and  in  some  cases  a  number  of  weeks, 
traversing  a  very  long  track.  Such  storms  in  Oriental 
seas  are  known  as  Typhoons.  Destruction  is  very  great 
when  one  of  them  moves  over  an  inhabited  island  or  drives 
great  sea  waves  upon  the  shores  of  a  continent. 

230.  Origin  of  terrestrial  winds. — The  trade- winds  and 
the  prevailing  westerlies,  or  broad  currents  from  west  to 
east  in  middle  latitudes,  belong  to  a  great  system  of  at- 
mospheric movements,  called  Terrestrial,  because  they  per- 
tain to  the  earth  as  a  whole.  Thunder-storms,  tornadoes, 
and  cyclones  are  local  disturbances  which  temporarily  in- 
terrupt the  uniformity  of  the  greater  movements. 

A  full  explanation  of  the  terrestrial  winds  would  be  out 
of  place  in  an  elementary  book,  but  the  two  great  facts 
on  which  they  depend  may  be  simply  stated  and  easily 
understood.  First,  the  regions  about  the  equator  are 
much  warmer  than  those  nearer  the  poles.  Hence  the  air 
is  lighter,  its  pressure  is  less,  and  the  colder  air  from  the 
north  and  south  pushes  in  and  crowds  it  up.     Great  vol- 


WINDS,  STORMS,  AND  CLIMATE 


267 


umes  of  warm  air  rise  in  the  doldrum  belt,  spread  out 
above,  and  flow  toward  the  poles.  Thus  there  is  a  great 
circulation  of  the  atmosphere,  toward  the  poles  above, 
toward  the  equator  below.  In  tropical  regions  these  lower 
currents  sweep  the 
surface  of  the  earth, 
constituting  the 
trade-winds,  but  in 
middle  latitudes  they 
flow  higher,  leaving 
space  beneath  them 
for  still  other  cur- 
rents, which  follow 
the  surface  and  tend 
poleward.  The  cur- 
rents are  shown  in 
Fig.  184,  where  the 
outer  band  repre- 
sents a  section  of  the 
atmosphere. 

The  second  great 
fact  is  the  deflection 
earth's  rotation.  The  rotation  aflects  the  direction  of 
every  body  moving  along  or  above  the  surface.  In  the 
northern  hemisphere  it  makes  moving  bodies  tend  to  curve 
toward  the  right,  whatever  the  direction  of  their  motion, 
and  in  the  southern  hemisphere  toward  the  left.  So  the 
trade-winds  north  of  the  equator,  being  turned  to  the  right 
of  their  southward  course;  flow  toward  the  southwest ;  and 
the  trade  winds  south  of  the  equator,  being  turned  to  the 
left  of  their  northward  course,  flow  toward  the  northwest. 
In  middle  latitudes  of  the  northern  hemisphere  the  lowest 
or  surface  winds  are  turned  to  the  right  from  their  north- 
ward course  and  flow  nearly  east,  and  the  corresponding 
winds  of  the  southern  hemisphere,  being  turned  to  the  left 
from  a  southward  course,  also  flow  nearly  east. 


Fig.  184.— The  prevailing  winds  of  the  globe  ;  with 
a  section  of  the  atmosphere  showing  its  system 
of  permanent  currents. 

or   turning  of   air- currents  by  the 


268    AN  INTRODUCTION  TO   PHYSICAL   GEOGRAPHY 

The  prevailing  winds  at  the  surface  of  the  earth  are 
shown  in  the  inner  part  of  Fig.  184.  All  winds  are  named 
after  the  directions  from  which  they  flow.  So  the  trade- 
winds  blowing  toward  the  southwest  are  called  the  north- 
east trades,  and  the  winds  blowing  toward  the  east  in  mid- 
dle latitudes  are  called  westerlies  (see  Section  221). 

Weather  and  Climate 

231.  Weather. — This  word  refers  to  the  state  of  the  at- 
mosphere. The  atmosphere  may  be  warm  or  cold,  wet  or 
dry,  still  or  moving,  cloudy  or  clear,  and  we  therefore  speak 
of  the  weather  as  hot,  or  sultry,  or  cold,  or  cloudy,  or  stormy, 
as  the  case  may  be.  If  the  condition  is  stable  for  days  or 
weeks,  we  speak  of  settled  weather,  or  if  it  is  changeable, 
we  characterize  the  weather  accordingly. 

We  not  only  speak  of  the  weather  and  describe  it  fully 
in  language,  but  we  record  it  upon  maps.  Temperature  is 
a  weather  element,  and  we  record  this  by  means  of  iso- 
therms (Sec.  216).  Barometric  pressure  is  another  weather 
element,  and  we  express  this  by  isobars.  In  like  manner 
arrows  represent  the  direction  of  winds.  Shaded  areas  tell 
where  there  is  rain  or  snow,  at  the  time  for  which  the  map 
is  made.  Other  features  may  be  shown,  but  these  are  the 
chief  things. 

232.  Weather  service  and  prediction. — For  about  thirty 
years  the  United  States  Government  has  maintained  a 
weather  service.  It  is  in  charge  of  the  Weather  Bureau,  a 
part  of  the  Department  of  Agriculture.  Each  morning  at  the 
same  hour  (eight  o'clock  in  the  East  and  five  o'clock  on  the 
Pacific  coast)  150  or  more  observers  record  the  various 
weather  elements  at  their  stations  and  send  the  results  by 
telegraph  to  Washington.  A  force  of  clerks  receive  the  facts 
and  record  them  on  weather  maps.  From  these  maps  experi- 
enced forecasters  determine  as  nearly  as  possible  what  the 
weather  will  be,  and  the  forecasts  are  sent  to  all  parts  of 


WINDS,   STORMS,   AND  CLIMATE  269 

the  country.  At  some  stations,  a  local  forecaster  receives 
such  reports  as  he  needs  and  makes  up  a  bulletin  for  his 
region.  The  forecasts  are  widely  published  in  newspapers, 
and  are  told  to  multitudes  of  people  by  the  display  of 
weather  signals  in  the  form  of  flags.  Special  warnings  are 
sent  to  seaports,  in  order  that  shipmasters,  knowing  the 
coming  of  dangerous  storms,  may  delay  in  putting  to  sea. 
The  coastwise  vessels  of  every  kind  greatly  profit  by  the 
weather  service.  The  coming  of  a  tropical  hurricane  from 
the  West  Indies  may  be  made  known  along  our  southern 
coast  in  time  for  protection  of  shipping  and  coastwise 
property.  The  advance  of  chilling  frosts  from  the  west 
and  north  into  the  fruit  regions  of  the  south  may  likewise 
be  foretold  in  some  cases.  Many  stations  are  maintained 
along  rivers,  from  which  the  data  as  to  rainfall,  melting  of 
snow,  and  other  changes  are  reported,  and  on  these  are 
based  forecasts  of  damaging  floods,  so  that  property  on  low 
grounds  may  be  removed  and  life  be  less  endangered. 

The  principal  predictions  of  the  weather  service  are 
possible  because  of  what  is  known  of  the  direction  and 
progress  of  the  great  cyclones  or  low  areas,  and  of  the  be- 
havior of  winds,  of  clouds,  and  rainfall  in  all  parts  of 
them,  ^o  two  cyclones,  indeed,  are  just  alike,  and  some 
depart  widely  in  rate  or  direction  from  the  usual  rate  or 
course,  so  that  mistakes  may  be  made,  but  the  service  as  a 
whole  has  demonstrated  its  value  to  the  people  of  the 
country,  and  is  sure  to  come  to  greater  completeness  and 
accuracy  in  the  future. 

Many  supposed  signs  of  the  weather  have  no  foundation 
in  fact.  Such  are  the  aspects  of  the  moon,  and  all  sayings 
about  the  relations  of  certain  days  of  the  month  or  season 
to  the  weather  that  will  follow.  On  the  other  hand,  old 
observers  of  the  weather  know  many  true  signs  of  w4nd, 
cloud,  and  sky,  which  give  them  shrewdness  in  prediction 
even  when  they  are  not  able  to  explain  or  assign  a  cause. 
By  long  habit  they  recognize  the  usual  order.     But  such 


270    AN  INTRODUCTION  TO   PHYSICAL   GEOGRAPHY 

foretelling  could  only  serve  for  one  locality,  and  could  in 
no  way  take  the  place  of  the  wide  view  provided  by  the 
Weather  Bureau. 

233.  Climate. — The  climate  of  a  region  is  the  sum  of  its 
weather.  It  includes  the  weather  of  the  succession  of  sea- 
sons for  a  succession  of  years.  A  year's  weather  follows 
the  general  course  of  all  years  for  the  special  region,  but 
may  be  quite  peculiar  in  some  respects.  Thus  in  the 
northern  United  States  we  occasionally  have  an  "  open " 
winter,  or  an  exceptionally  hot  summer,  or  abnormally 
heavy  snows.  Hence  a  period  of  years  is  necessary  for  a 
full  knowledge  of  climate.  Like  the  weather,  climate  is 
described  according  to  its  most  important  or  striking  fea- 
tures. Thus  climate  may  be  dry,  wet,  cold,  temperate  or 
hot,  uniform  or  subject  to  great  extremes.  Or  we  may  de- 
scribe climate  by  its  relations  to  man,  as  healthful  or  the 
contrary,  as  bracing  or  enervating,  as  agreeable  or  un- 
pleasant. 

234.  Climates  of  the  TTnited  States. — We  use  the  plural 
here,  because  our  country  covers  so  many  degrees  of  lati- 
tude, ranges  so  far  from  coast  to  interior,  and  has  such 
a  variety  of  lowland  and  upland,  that  a  variety  of  climates 
is  the  result.  We  are  wholly  in  the  Xorth  Temperate  zone, 
and  therefore  a  temperate  climate  is  more  common  than 
any  other.  But  along  our  South  Atlantic  and  Gulf  borders 
tropical  conditions  prevail.  There  is  a  wide  difference, 
however,  between  the  Carolina  coasts  and  the  cool  uplands 
of  the  southern  Appalachians.  An  isothermal  line  will 
sometimes  run  from  Massachusetts  southwest  in  the  eastern 
border-  of  the  Appalachian  highlands,  into  Georgia,  and 
then  double  sharply  back  on  the  west  of  the  uplands  as  far 
north  as  the  Great  Lakes,  before  turning  to  the  west. 
Thus  the  wedge  of  mountains  with  cooler  air  is  driven  far 
down  between  the  warm  areas  of  the  Atlantic  on  the  one 
hand  and  the  lower  Mississippi  on  the  other.  Even  a 
sharper  contrast  is  seen  if  we  compare  the  high  Sierras  of 


WINDS,  STORMS,  AND  CLIMATE 


271 


California,  with  their  snows  and  glaciers,  with  the  warm 
central  valley  and  Pacific  shore  of  the  same  State.  Or  we 
may  compare  the  same  mountains  with  the  driest  and  hot- 
test region  of  the  United  States,  in  southern  California, 
Nevada,  and  Arizona. 

A  most  important  fact  of  climate  in  the  United  States 
is  the  prevalence  of  the  great  cyclonic  and  anticy clonic 
storms,  and  a  strong  swing  between  winter  and  summer 
conditions,  especially  in  northern  districts.  Thus  in  the 
summer  the  areas  of  low  and  high  pressure  follow  each 
other  across  the  continent  from  the  west  to  the  northeast, 
giving  an  alternation  of  hot  waves  and  cooler  spells.  In 
winter  these  alternations  are  still  stronger,  giving  us  violent 


iiMd. 


Fig.  185.— a  vineyaid  in  oouunjiu  California,  where  rainfall  is  so  small  that  ciops 
must  be  irrigated.  The  field  is  traversed  by  a  system  of  ditches  into  which  water 
from  a  stream  is  run  several  times  during  the  growing  season. 


winter  storms,  followed  by  cold  waves,  with  clear  skies  and 
zero  temperatures.    Only  in  Florida  and  along  the  Gulf  and 
California  coasts  are  the  contrasts  subdued  by  the  presence 
of  the  ocean. 
19 


272    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

Almost  as  often  as  by  heat  and  cold,  we  describe  the 
climates  of  our  country  according  to  the  amount  of  rainfall. 
Here  we  need  do  little  more  than  refer  the  student  to  the 
section  on  that  subject  (208).  Throughout  the  north,  the 
winter  precipitation  is  mainly  in  the  form  of  snow.  This 
being  a  poor  conductor,  keeps  the  ground  from  freezing  as 
deeply  as  it  otherwise  would,  serving  as  a  blanket  to  retain 
the  heat  already  received.  On  the  other  hand,  the  sun's 
heat  is  lost  by  reflection  from  its  surface,  and  the  winter  cold 
is  thus  increased.  All  the  eastern  region  is  well  watered. 
Over  the  prairies  the  rainfall  diminishes,  but  is  abundant 
for  plants  until  we  reach  the  semiarid  belt  in  eastern  Da- 
kota, eastern  Nebraska,  and  central  Kansas.  Beyond  that 
region  the  arid  belt  begins,  with  less  than  20  inches.  There 
the  most  important  problems  are  how  to  store  up  and  save 
the  waters  of  storms  and  streams,  and  how  best  to  use 
them  in  irrigating  the  lands. 

235.  Climates  of  other  lands. — Space  will  not  permit  of 
any  complete  account  of  the  climates  of  the  world.  In 
describing  the  distribution  of  rainfall  and  the  winds  and 
storms  of  the  globe,  much  information  has  been  given  con- 
cerning climate.  It  is  more  important  that  the  student 
should  grasp  the  principles  which  control  climate,  than 
that  he  should  here  find  a  systematic  account  of  climates. 
A  restatement  of  some  of  these  principles  follows. 

Difference  in  latitude,  and  the  resulting  differences  in 
the  amount  of  heat  received  from  the  sun,  give  us  the  basis 
for  climate.  The  inclination  of  the  earth's  axis,  causing 
the  succession  of  seasons  and  an  alternation  of  seasons  in 
the  two  hemispheres,  is  the  next  great  principle.  The  dis- 
tribution of  land  and  water  introduces  other  great  changes 
into  the  climates  which  latitude  would  give.  This  is  strik- 
ingly seen  in  the  North  Atlantic,  with  its  currents  carrying 
warm  water  against  the  Gulf  shores,  and  drifting  thence 
upon  the  shores  of  Europe,  giving  mild  climates  in  Great 
Britain  and  Germany,  which  have  the  latitude  of  Labrador. 


WINDS,   STORMS,   AND  CLIMATE  273 

As  a  further  principle,  the  atmospheric  circulation  of  the 
globe  gives  us  the  trade-wind  climates  of  the  tropics,  with 
their  occasional  hurricanes,  and  the  monsoons  of  the  East, 
with  strong  periodic  winds  and  rains.  We  refer  again  to 
the  all-important  fact  of  temperate  latitudes,  the  prevail- 
ing westerlies,  with  their  cyclones,  anticyclones,  occasional 
tornadoes,  and  frequent  summer  thunder-storms.  We  ob- 
serve again  the  fact  of  "  continental "  or  dry  interior  cli- 
mates, with  wet  sea-borders,  as  shown  in  nearly  all  conti- 
nents, and  seen  in  a  conspicuous  way  if  we  compare  the 
Great  Plains  with  the  Pacific  Coast,  the  Central  Plateau  of 
Asia  with  India,  or  Central  Australia  with  the  most  of  its 
shore  regions.  Finally,  we  observe  the  effect  of  altitude 
on  climate  when  we  see  the  cool  summits  of  the  Adiron- 
dacks  rising  from  the  warmer  lands  about  Lake  Ontario, 
observe  the  Eocky  Mountain  snow-fields  from  Colorado 
Springs,  or  see  the  wintry  Alps  towering  above  the  warm 
lowlands  of  Italy. 


CHAPTEE  XII 

THE    EARTH'S  MAGNETISM 

236.  The  compass. — Consider  for  a  moment  how  we  find 
our  way  from  place  to  place.  Often  we  follow  a  road  or 
path.  To  cross  a  field  we  select  some  object  beyond,  and 
walk  toward  it.  The  traveler  on  a  prairie,  or  in  a  forest, 
may  notice  which  way  his  shadow  falls,  and  guide  himself 
by  that.  But  if  clouds  hide  the  sun,  that  aid  fails  him,  and 
he  takes  the  Compass.  The  compass  needle  points  toward 
the  north ;  and  if  he  knows  which  way  north  lies  he  can 
easily  lay  out  a  course  toward  the  east  or  west,  or  in  whatever 
direction  he  desires.  Such  a  guide  is  peculiarly  useful  on 
the  sea,  where  neither  pathway  nor  distant  object  can  be 


Fig.  186.— a  magnetic  needle,  with  a  cross-section  to  show  the  mode  of  hanging. 
P,  pivot ;  A,  cap  of  agate  with  hollow  beneath  to  rest  on  the  pivot ;  W,  adjust- 
able weight  to  counteract  the  dipping  tendency  (page  277). 

seen.  Though  sun  and  stars  are  hidden  for  many  days,  the 
mariner  pushes  boldly  forward,  steering  always  as  the  com- 
pass directs,  and  knowing  it  will  not  send  him  astray. 

The  compass  is  a  rod  or  "  needle  "  of  magnetized  steel, 
balanced  on  a  pivot  so  as  to  be  free  to  swing  to  the  right 
or  left.  Like  other  magnets,  it  has  two  poles,  named  north 
and  south.  In  the  instrument  made  for  the  mariner  sev- 
eral such  needles  are  placed  side  by  side,  and  all  are  fast- 
274 


THE   EARTH'S  MAGNETISM 


2Y5 


Fig.  187.— The  compass  card.  Reciting:  the 
names  of  the  32  points  is  called  by  sail-/ 
ors  "  boxing  the  compass." 


ened  to  the  under  side  of  a  circular  card,  which  may  be 
either  balanced  on  a  pivot  or  floated  on  a  liquid.  On  top 
of  the  card  is  a  printed 
rosette  or  star  with  32  rays, 
each  indicating  a  direc- 
tion, or  "  point  of  the  com- 
pass "  (Fig.  187). 

237.  Magnetic  declina- 
tion.— While  Columbus  was 
sailing  westward  in  search 
of  the  Indies,  and  before 
he  had  found  the  ^N^ew 
World,  he  made  another 
discovery,  and  one  equally 
unexpected.  He  found 
that  the  needle,  instead 
of  pointing  steadfastly 
toward  the  north  star,  swung  to  one  side,  and  the  farther 
he  went  the  greater  its  error.  This  was  by  no  means  a 
welcome  discovery,  for  it  weakened  confidence  in  a  faith- 
ful friend,  and  seemed  an  evil  omen  to  his  superstitious 
sailors.  But  it  led  to  a  better  knowledge  of  the  mag- 
netic needle,  and  this  has  been  of  great  value  to  man- 
kind. The  difference  between  the  pointing  of  the  compass 
and  the  direction  of  true  north,  or  the  Magnetic  Declina- 
tion, has  now  been  measured  at  many  places  and  at  many 
times,  and  maps  have  been  made  to  show  its  distribution. 
These  maps  are  of  two  kinds,  illustrated  by  Figs.  188  and 
189.  In  Fig.  188  the  lines  show  by  their  directions  the 
positions  taken  by  the  needle  at  different  places.  Thus, 
where  one  of  them  crosses  Massachusetts,  near  the  meridian 
of  70°  west  longitude,  it  is  evident,  by  comparing  its  direc- 
tion with  the  meridian,  that  the  needle  points  west  of  north. 
Its  direction  is  still  more  to  the  west  in  Labrador  and 
Greenland.  But  along  the  Mississippi  River  it  points  a 
little  east  of  north,  while  the  declination  to  the  east  is  large 


2Y6    AN  INTEODUCTION  TO  PHYSICAL  GEOGRAPHY 

in  California  and  Alaska.  The  lines  of  this  system  are 
known  as  Magnetic  Meridians.  If  we  should  start  with  a 
compass  in  hand  and  travel  steadily  in  the  direction  in 
which  it  pointed  we  should  follow  a  magnetic  meridian, 
and  should  eventually  be  brought  to  a  place  inside  the 
arctic  circle  where  all  these  meridians  meet.  This  place  is 
the  IS'orth  Magnetic  Pole  of  the  earth,  and  is  nearly  20° 
distant  from  the  geographic  pole.  There  is  a  similar  point, 
the  South  Magnetic  Pole,  within  the  antarctic  circle. 


Fig.  189.— Isogonics,  or  lines  of  equal  magnetic  declination,  for  the  United  States 

in  1902. 

Fig.  189  shows  the  same  facts,  more  in  detail,  for  the 
United  States,  but  shows  them  by  a  very  different  set  of 
lines.  It  will  be  remembered  that  a  map  contour  runs 
through  all  points  having  the  same  height  above  the  sea, 
and  that  an  isobar  shows  the  line  along  which  the  air  pres- 
sure is  everywhere  the  same.  In  like  manner  the  lines  of 
this  map  pass  through  points  at  which  the  declination  of 
the  needle  is  the  same.  Thus,  a  line  crossing  Texas,  Okla- 
homa, Kansas,  Nebraska,  South  Dakota,  and  Minnesota  in- 
cludes all  points  at  which  the  needle  turns  10°  to  the  east 


Fig.  188.— Magnetic  meridians  for  North  America  in  1885.    (See  page  275.) 


THE  EARTH'S  MAGNETISM  277 

of  north.  The  line  next  east  of  it  stands  for  an  eastward 
turning  of  9°,  and  at  any  locality  in  the  belt  between  the 
two  lines  the  declination  of  the  needle  is  between  9"  and 
10°.  The  "  line  of  no  declination  "  crosses  a  belt  of  States 
from  Michigan  to  South  Carolina,  and  east  of  it  the  needle 
turns  toward  the  west.  These  lines  are  called  "  isogonics  " 
(equal  angles).  From  an  isogonic  map  the  mariner  and 
surveyor  learn  how  much  allowance  to  make  for  the  differ- 
ence between  "  magnetic  north  "  and  true  north. 

The  declination  varies  not  only  from  place  to  place,  but 
from  time  to  time.  Fortunately  the  change  with  time  is 
slow,  so  that  a  good  magnetic  map  is  serviceable  for  many 
years.  The  magnetic  meridians  in  Fig.  188,  which  were 
made  for  the  year  1885,  are  not  strictly  accurate  now.  The 
isogonics  in  Fig.  189  represent  the  latest  work  of  the  Coast 
Survey,  the  bureau  charged  by  the  Government  with  mag- 
netic surveys. 

238.  The  magnetism  of  the  earth. — Every  magnet  has  an 
influence  on  other  magnets  when  they  are  brought  near. 
It  is  very  instructive  to  lay  a  strong  magnet  on  a  table  and 
then  move  a  compass  about  it.  The  needle  changes  its 
direction  with  every  change  of  position,  now  pointing  to- 
ward the  magnet,  now  from  it,  and  now  lying  parallel ;  or, 
in  other  words,  it  is  controlled  by  the  magnet.  Now,  as 
the  compass  shows  similar  changes  of  direction  when  it  is 
moved  from  one  position  to  another  about  the  earth,  the 
conclusion  has  been  reached  that  the  earth  also  is  a  mag- 
net. In  comparison  with  its  size  it  is  not  a  strong  magnet, 
but  its  strength  is  sufficient  for  the  guidance  of  those  who 
must  journey  without  beaten  paths — the  explorer  and  the 
navigator. 

239.  Dip. — The  compass  needle  can  swing  to  the  right 
or  left.  If  it  were  hung  so  that  it  could  swing  up  or  down 
it  would  usually  not  lie  level,  but  slant,  or  "  dip,"  in  one 
direction  or  the  other.  A  needle  thus  hung  is  called  a  dip 
needle,  and  is  said  to  show  the  Magnetic  Dip.     At  the 


2Y8    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

magnetic  equator  it  lies  level.  Carried  northward,  it  turns 
its  north  end  more  and  more  downward,  until  at  the  raag- 
netic  pole  it  points  toward  the  center  of  the  earth.  Carried 
southward,  its  south  end  is  turned  downward,  and  it  be- 
comes vertical  with  its  north  end  upward  at  the  south 
magnetic  pole.  Fig.  190  shows  the  dip  all  about  the  globe. 
Close  to  the  magnetic  poles  the  magnetic  force  is  all  ver- 
tical, and  the  compass  will  not  act.  It  is  therefore  fortu- 
nate that  these  poles  are  in  regions  unsuited  to  man. 


North  Magnetic  Pole     ^^/   II,  '     —^  South  Magnetic  Pole 

Fig.  190.— Positions  of  the  dip  needle  at  various  points  about  the  globe. 

There  is  a  kind  of  iron  ore  which  is  magnetic,  and  frag- 
ments of  it,  called  lodestones,  were  the  first  compasses. 
Large  masses  of  this  ore  are  contained  in  the  rocks  about 
Lake  Superior,  and  they  are  able  to  swing  the  compass  and 
dip  needle  out  of  their  regular  positions.  Those  instruments 
have  therefore  been  used  in  searching  for  this  ore,  and 
valuable  mines  have  been  located  in  this  way. 


CHAPTEE  XIII 

THE  OCEAN 

We  now  pass  from  the  Lands  and  the  Atmosphere  to 
the  study  of  the  third  great  feature  of  the  physical  world, 
the  Ocean.  To  mankind  it  is  an  essential  feature,  for  land 
life  could  not  exist  without  it.  A  "good  round  ball  of 
meadow  and  plowland "  would  be  impossible.  We  must 
see  what  the  ocean  is  and  what  it  does. 

240.  Ocean-basins.— We  give  this  name  to  those  low 
parts  of  the  earth's  surface  which  are  covered  by  ocean 
waters,  and  we  think  of  the  lands  as  making  rims  about 
them.  The  student  must  not  forget  that  an  ocean-basin  is 
vastly  broad  as  compared  with  its  depth,  and  that  its  bot- 
tom is  not  a  plane  but  a  part  of  the  surface  of  a  sphere. 
Either  the  top  or  the  bottom  of  the  sea  may  be  thought  of 
as  a  part  of  the  surface  of  the  round  earth.  The  ocean 
may  be  likened  to  a  film  of  liquid  clinging  to  the  outside  of 
a  spoon. 

We  have  already  seen  (Sec.  5)  that  all  the  oceans  may 
be  truly  regarded  as  one.  In  no  strict  sense  can  we  speak 
of  several  basins.  The  American  continents  do  indeed 
separate  the  Atlantic  and  Pacific,  but  there  is  no  division 
between  either  and  the  so-called  Antarctic  Ocean.  The 
same  is  true  of  the  Indian  Ocean  and  the  Antarctic,  and  in 
some  degree  of  the  Arctic  and  Atlantic  Oceans.  It  is  bet- 
ter to  think  of  the  waters  as  forming  a  spherical  sheet  over 
nearly  three-fourths  of  our  planet,  and  broken  by  a  few 
large  and  many  small  bodies  of  land. 

The  sea-floor,  as  it  is  often  called,  is  in  general  quite 

279 


280    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

smooth,  as  compared  with  the  land.  It  has  mountains,  but 
they  have  still  the  simplicity  of  shape  with  which  they  were 
uplifted,  and  are  not  cut  into  a  thousand  crags  and  gorges, 
as  on  land.  It  has  also  many  volcanoes,  great  and  small, 
and  these  too  are  unworn.  Between  and  about  such  moun- 
tains and  hills  is  spread  an  ever-growing  sheet  of  sediment 


Fig  191  —Western  part  of  the  Atlantic  basin.  This  map  was  made  by  photograph- 
ing a  model,  in  which  the  scale  of  heights  was  many  times  greater  than  the  scale 
of  distances. 

— partly  the  waste  from  the  land,  delivered  at  the  sea-bor- 
der by  streams,  partly  the  myriad  shells  of  small  ocean  crea- 
tures (page  300).  Of  such  fine  deposits  vast  plains  are 
made,  smoother  than  the  prairies  of  the  Mississippi  Valley. 


THE  OCEAN  281 

Much  of  the  Atlantic  Ocean  is  15,000  to  20,000  feet 
deep.  Eunning  in  a  generally  north  and  south  direction 
through  it  is  a  gentle  swell  of  the  floor,  over  which  the 
water  is  about  12,000  feet  deep.  The  slope  from  deeper  to 
shallower  parts  is  so  gentle  that  the  eye  could  not  detect 
any  variation  from  a  perfectly  level  plain.  The  deepest 
point  thus  far  sounded  marks  27,366  feet  and  lies  near 
Porto  Eico. 

The  average  depth  of  the  Pacific  Ocean  is  greater  than 
that  of  the  Atlantic,  being  2f  miles.  At  least  two  sound- 
ings of  more  than  30,000  feet  have  been  made,  one  near  the 
Ladrone  Islands  and  the  other  not  far  from  New  Zealand. 
Thus  the  greatest  known  depth  of  the  ocean  about  equals 
the  greatest  known  height  of  land,  that  of  Mount  Everest, 
the  measure  in  each  case  being  nearly  six  miles.  This  total 
unevenness  of  about  12  miles  nearly  equals  the  amount  of 
flattening  of  the  earth  at  either  pole.  In  this  flattening, 
and  in  the  difference  between  sea-bottoms  and  mountains, 
we  have  the  chief  departures  of  the  earth's  crust  from  the 
form  of  a  sphere. 

241.  Continental  shelves. — Thus  far  we  have  considered 
only  the  deeper  parts  of  the  ocean-basins.  But  the  deep 
seas  do  not  commonly  come  close  to  the  shore-line.  For 
many  miles  offshore,  soundings  often  show  but  a  few  score 
or  a  few  hundred  feet.  This  is  the  case  along  our  Atlantic 
coast.  Shallow  water  surrounds  Newfoundland,  and  a  belt 
of  shallow  sea  50  to  100  miles  wide  runs  past  Nova  Scotia, 
New  England,  and  down  to  Florida.  A  very  smooth  bottom 
slants  gently  down  to  depths  of  about  100  fathoms.  Then 
there  is  a  rapid  descent  to  the  deep  bottom  of  the  Atlantic. 
The  relief  map  (Fig.  191)  and  the  cross  profile  (Fig.  192) 
show  these  features.  This  slightly  submerged  belt  is  called 
a  Continental  Shelf,  because  it  seems  a  true  part  of  the 
continental  block,  rising  above  the  deep  bottoms.  The  sea 
laps  over  upon  the  edges  of  the  great  land  masses. 

Our  last  statement  implies  that  continental  shelves  are 


282    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

common.  Our  Atlantic  shelf  can  be  traced  around  south- 
ern Florida  and  all  about  the  Gulf  of  Mexico,  except  where 
it  is  pierced  by  the  Yucatan  channel  and  by  the  deep  pas- 
sage which  carries  the  Gulf  Stream  between  Florida  and 


1 1 

S  2 


S  i 
5  °- 


Continental 
Shelf 


mf^mm^^^y^ 


^/:^///- 


Ocean  I c 


Basin 


'///^ 


/>; 


'MMmmimm^ 


i^A/Z}??P7:77777r, 


Fig.  192.  -Profile  of  the  bottom  of  the  Atlantic  Ocean  and  adjoining  land  in  New 
Jersey  and  Pennsylvania,  showing  the  continental  shelf.  Scale  of  distances, 
1  inch  =  140  miles.    Scale  of  heights,  1  inch  =  7  miles. 


Cuba.  Another  continental  shelf  is  found  on  the  European 
side.  It  extends  to  the  westward  of  the  British  Islands. 
Soundings  show  shallow  waters  in  the  North  Sea,  the  Eng- 
lish Channel,  the  Irish  Sea,  and  west  of  Scotland  and  Ire- 
land. In  other  words,  these  islands  rise  from  a  platform 
which  is  but  slightly  overflowed  by  the  ocean  waters. 

242.  Mediterranean  seas. — The  water  of  the  Strait  of 
Gibraltar  is  but  1,200  feet  deep.  But  the  sea  within  has 
depths  of  13,000  feet.  As  it  lies  between  two  continents, 
the  name  Mediterranean  (between  lands)  has  been  given  to 
it.  It  does  not  lie  in  a  basin  cut  out  of  the  land,  but  in  a 
basin  made  by  the  rising  of  the  lands  around  it.  The  con- 
tinents have  grown  up  about  a  part  of  the  ancient,  open 
sea.  On  a  smaller  scale  the  same  is  true  of  the  Black  Sea, 
and  even  of  the  Caspian,  though  the  latter  has  no  connec- 
tion with  the  ocean.  The  Caribbean  Sea  and  the  Gulf  of 
Mexico  are  also  mediterraneans. 

243.  Islands  in  the  ocean.— We  might  call  the  greater 
lands  islands,  because  they  are  washed  on  every  hand  by 
the  seas ;  but  we  agree  to  call  them  continents.  The 
origin  of  the  continents  and  greater  islands  is  too  difficult 


THE  OCEAN 


283 


a  subject  for  elementary  study,  but  the  growth  of  many 
smaller  islands  can  be  better  understood. 

Hundreds  of  these  small  lands  are  due  to  volcanoes  dis- 
charging at  the  bottom  of  the  sea,  gradually  building  their 
cones  of  lava  and  ash  to  the  water-level,  and  even  many 
thousands  of  feet  above.  These  form  the  principal  in- 
equalities «f  the  ocean-basins.  Detailed  soundings  over 
all  the  seas  would  show  their  submerged  crests  at  all  depths. 
In  the  Atlantic,  the  Azores,  the  Canary,  and  St.  Helena 
are  among  those  that  have  grown  above  the  sea  surface. 
In  the  Pacific  such  shoals  and  islands  are  to  be  numbered 
by  hundreds  or  thousands.  The  Hawaiian  Islands  (Sec. 
183)  are  among  the  largest  and  loftiest. 

Around  the  borders  of  many  of  these  volcanic  is- 
lands, fields  of  coral  flourish  in  the  shallow  waters.  The 
coral  is  an  animal  of 
low  order,  consist- 
ing of  little  more 
than  a  sack  or  hol- 
low body,  with  a 
mouth  at  the  top, 
surrounded  by  a 
fringe  of  simple 
arms  or  feelers.  It 
is  attached  to  the 
mud  or  rocks  of 
the  bottom,  and 
often  great  num- 
bers of  these  sim- 
ple forms  are  crowded  together  on  twig -like  branches, 
formed  of  the  calcium  carbonate  which  they  take  from  the 
sea-water.  In  color  and  form  they  look  more  like  flowers 
than  animals.  The  waves  often  break  and  grind  to  pieces 
the  skeletons  of  these  lowly  forms  and  make  coral-mud. 
In  the  shallow  seas  about  the  islands,  therefore,  are  fields 
of  living  coral  and  floors  of  coral  fragments  and  mud. 


Fig.  193.— a  coral  from  the  Fiji  Islands.     The  flower- 
like parts  are  the  living  animals. 


284    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

Such  a  field  is  a  coral  reef,  and  when  it  borders  an  island 
it  is  called  a  fringing  reef. 

Sometimes  a  belt  of  water  lies  between  the  high  island 
and  a  low,  long  island  which  is  of  coral  making.  On  the 
seaward  side  of  this  offshore  island  the  corals  are  growing. 
Here  we  have  a  barrier  reef,  with  a  lagoon  of  protected 
water.     In  other  cases,  low  coral  islands  and  reefs  form  a 


Pig.  194. — ^A  coral  reef  at  low  tide ;    part  of  the  Great  Barrier  Reef,  off  the  coast 

of  Australia. 


rude  circle  or  loop,  with  a  shallow  basin  of  quiet  water 
within.  Corals,  as  before,  thrive  all  about  the  outside  in 
the  shallow  water,  while  the  coral  sand,  heaped  by  waves 
and  winds,  forms  the  low  islands,  clad  with  palms  and  other 
tropical  plants.  Such  a  bracelet  of  low  islands  is  an  Atoll. 
The  student  should  remember  two  or  three  important 
facts  about  corals.     They  are  not  "  insects,"  but  are  far 


THE  OCEAN 


below  these  creatures  in  their  rank  as  animals.     They  have 
no  instinct  which  prompts  them  to  build  islands.    They  do 


Fig.  195.— a  volcanic  island  encircled  by  a  barrier  reef  and  lagoon. 

not  work  from  the  bottom  of  the  sea.  Most  of  them  can 
not  live  below  a  few  hundred  feet  of  depth.  That  they 
"  build  "  anything  is  wholly  due  to  the  crushing  and  push- 


FiG.  196.— An  atoll. 


ing  of  their  remains  by  waves  and  winds.     And  finally, 
they  can  only  live  in  water  having  temperatures  of  68°  or 


286    AK  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

more.  Hence  they  are  never  found  far  from  the  tropics. 
The  Bermudas  are  the  most  northerly  of  coral  islands. 
The  Galapagos  Islands,  close  to  the  equator  in  the  Pacific 
Ocean,  have  no  bordering  reefs,  because  ocean  currents 
bring  cold  water  from  the  southern  seas. 

244.  Composition  of  sea-water. — The  waters  of  the  ocean 
contain  much  material  which  is  also  found  in  a  solid  state 
in  the  rocks  of  the  earth's  crust.  These  solids  in  solution 
make  about  3J  per  cent,  of  the  ocean  waters.  Much  the 
greatest  part  of  this  is  common  salt.  Far  less  in  quantity 
is  calcium  carbonate.  This  is  important,  however,  for 
many  sea  animals  form  shells  of  it.  The  gases  which 
make  up  the  atmosphere  are  minutely  distributed  through 
sea-water.  The  oxygen  held  in  the  sea  makes  life  possible 
even  at  great  depths,  but  deep-sea  animals  get  very  little 
of  it,  and  their  life  is  probably  sluggish.  Some  forms,  as 
the  whales,  must  come  up  to  the  surface  to  breathe. 

The  ocean  is  more  salty  in  some  places  than  in  others. 
In  a  nearly  closed  sea,  like  the  Baltic,  where  much  water 
comes  in  from  the  land,  and  does  not  freely  spread  to  the 
open  ocean,  the  water  is  partly  fresh,  and  is  called  "  brack- 
ish." This  has  the  effect  of  diminishing  the  size  of  some 
shelled  creatures  whose  tribes  have  lived  in  these  waters  a 
long  time.  Other  enclosed  seas,  where  evaporation  is  great 
and  the  influx  of  streams  small,  are  much  more  salty  than 
the  open  ocean.  This  is  true  of  parts  of  the  Mediterranean. 
And  in  tropical  regions  of  the  Atlantic  there  is  more  salt 
than  in  the  arctic  seas.  Fresh  water  is  lighter  than  salt ; 
hence  the  waters  of  a  great  river  like  the  Mississippi  or 
Amazon  will  flow  out  over  the  salt  water  and  freshen  the 
surface  parts  of  the  sea  for  long  distances  from  the  shore. 

The  salt-beds  found  in  the  rocks  are  due  to  the  evapora- 
tion of  waters  in  shallow,  land-locked  basins  of  the  ancient 
seas.  They  were  natural  evaporating-pans,  heated  by  the 
sun.  Common  mud  afterward  drifted  in  over  them,  and  so 
the  layers  of  salt  and  rock  were  formed.      The  sea  has 


THE  OCEAN  287 

always  been  salty,  and  it  is  constantly  receiving  through 
the  rivers  whatever  the  waters  dissolve  from  the  rocks  of 
the  lands. 

245.  Temperature  of  the  ocean.  —  The  surface  waters 
are  warm  in  the  tropics,  cooler  in  temperate  latitudes, 
and  cold  in  the  polar  regions.  Thus,  in  a  general  way, 
they  are  like  the  lands.  Near  the  equator  about  80°  is 
the  prevailing  temperature.  Some  closed  seas,  like  the 
Eed  and  the  Persian  Gulf,  attain  almost  to  blood-heat. 
In  the  polar  regions  the  temperatures  go  down  to  the 
freezing-point  of  28°  or  29°,  varying  with  the  amount  of 
salt  in  the  water. 

Comparatively  warm  waters  push  into  northern  and 
southern  regions  by  means  of  ocean  currents,  and  cold 
waters  invade  temperate  latitudes  in  the  same  manner. 
Such  cold  drifts  come  from  Greenland  into  the  Atlantic, 
often  floating  chilling  fleets  of  icebergs. 

The  student  should  notice  that  we  have  spoken  only  of 
the  surface  temperatures  ;  we  are  now  ready  for  the  impor- 
tant statement  that  no  such  wide  diiferences  are  found  in 
the  temperature  of  the  deep  waters  in  different  latitudes. 
The  sun's  rays  aflect  only  the  surface  waters.  Even  in  the 
torrid  zone  the  bottom  waters  are  always  cold,  having  tem- 
peratures of  35°  to  40°.  There  is  a  considerable  drift  of 
surface  waters  from  low  to  high  latitudes.  On  the  con- 
trary, the  water  from  north  and  south  slowly  creeps  toward 
the  equator  in  the  depths.  This  accounts  for  the  coldness 
of  the  deep  waters  everywhere. 

246.  Light  and  color. — The  prevailing  hue  of  the  sea  is 
blue.  But  those  who  have  sojourned  by  it  or  sailed  over  it 
know  how  various  are  its  colors.  Offshore  the  waters  are 
often  tinged  with  the  muds  that  have  floated  out  from  the 
land.  The  blue  of  the  saltier  parts  is  specially  deep.  The 
Gulf  Stream  is  thus  distinguished  from  the  less  salty  Lab- 
rador current ;  and  the  Japan  current  is  called  Kuro  Shiwo 
(black  water).     In  mid-ocean  myriads  of  creatures  may 

30 


288    AN  INTRODUCTION  TO   PHYSICAL   GEOGRAPHY 

send  forth  a  phosphorescent  glow  that  seems  to  touch  the 
sea  with  fire. 

247.  Movements  of  the  ocean  waters. — Even  in  the  deep- 
est calm  the  ocean  is  never  perfectly  still.  It  is  more 
fixed  than  the  changeful  sea  of  air  above  it,  and  less  stable 
than  the  lands  that  border  it.  But  even  the  lands  are 
never  twice  quite  the  same,  and  so,  from  beginning  to  end, 
geography  deals  with  an  unfolding  world.  The  movements 
of  the  sea  fall  into  three  classes.  Waves,  Tides,  and  Currents. 
We  shall  study  them  in  this  order. 

248.  Waves. — The  winds  ruffle  the  surface  and  make  a 
series  of  ridges  and  furrows.  The  summit  line  of  a  single 
wave  is  its  Crest  and  the  furrow  is  the  Trough.  Under  a 
moderate  wind  the  crest  will  be  a  few  feet  higher  than  the 
trough.  In  storms  the  waves  may  be  20  or  30  feet  high. 
In  powerful  storms  the  height  may  rise  to  40  or  50  feet. 
Even  great  ships  must  be  guided  across  the  crests  of  such 
waves,  or  be  overturned  by  the  rolling  motion.  Wave 
motion  ceases  a  few  hundred  feet  below  the  surface,  for 
the  winds,  like  the  sun,  can  not  affect  the  deeper  waters. 

The  student  will  remember  that  even  a  small  steamer 
may  raise  waves  astern,  and  that  a  gentle  swell  may  after- 
ward be  felt  at  some  distance,  if  we  cross  the  track  of  the 
steamer  in  a  small  boat.  On  a  larger  scale  the  wave 
motion  in  a  region  of  ocean  storm  is  passed  on  and  may 
create  a  swell  in  otherwise  quiet  seas,  thousands  of  miles 
away. 

Waves  may  be  studied  conveniently  on  a  pond  which  is 
stirred  by  the  wind.  Drop  a  twig  in  the  water,  and  observe 
its  motions.  It  may  drift  slowly,  but  does  not  travel  so 
fast  as  the  waves.  As  each  wave  passes,  it  rises  and  falls ; 
on  the  crest  it  moves  a  little  forward,  in  the  trough  a  little 
back.  The  motion  of  the  twig  is  also  the  motion  of  the 
particles  of  water  about  it,  and  it  shows  their  motion  to  the 
eye.  The  wave  is  not  a  body  of  water  gliding  forward,  like 
a  current,  but  a  traveling  shape  of  water.     A  field  of  grain 


THE  OCEAN 


289 


swaying  in  the  summer  wind  shows  how  the  sea  may  keep 
its  place  while  the  wave  moves  on. 

While  urged  by  the  wind,  the  larger  waves  sometimes 
break  and  whiten  at  the  crest,  even  in  the  open  sea,  and 
nearly  all  waves  break  at  the  shore.  As  a  wave  moves 
through  shallow  water 
near  the  shore,  the  crest 
goes  faster  than  the 
base,  the  front  becomes 
steeper,  and  finally  the 
crest  falls  forward  in  a 
cascade  (Fig.  197).  This 
tumbling  crest  is  a 
breaker.  As  the  ad- 
vancing cascade  looks 
like  a  turning  cylinder, 
the  term  Eollers  is 
sometimes  used.  If  the 
bottom  descends  slowly, 
a  series  of  waves  may  be  seen  thus  breaking,  the  water  of 
the  inshore  breakers  rushing  up  the  slopes  of  the  strand. 
This  water  pours  back  by  a  swift  flow  along  the  bottom, 
under  the  onrushing  surface  waters,  and  is  known  as  the 
Undertow,  so  dangerous  to  bathers  in  the  surf.  The 
changes  which  waves  cause  along  the  shore  will  be  de- 
scribed in  the  next  chapter. 

If  a  strong  earthquake  happens  under  the  sea,  a  shock 
may  be  communicated  to  the  waters,  and  great  waves  may 
be  raised.  The  term  tidal  should  not  be  applied  to  these 
waves.  In  some  parts  of  the  world,  as  Japan  and  Chile,  such 
waves  have  rushed  in  over  the  coastal  lands,  overwhelmed 
cities,  and  stranded  men-of-war  and  other  vessels  at  some 
distance  inland.  Such  a  wave  travels  swiftly  across  the 
seas  as  a  broad  swell,  and  breaks  with  destructive  force  at 
the  shore.  The  Lisbon  shock  in  1755  sent  forth  a  wave 
that  deranged  shipping  and  flooded  streets  of  an  Irish  port, 


Fig.  197.— Surf,  on  a  beach  of  sand  and  gravel. 


290    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

while  the  shaking  that  accompanied  the  eruption  of  Kra- 
katoa  (Sec.  184)  in  1883  caused  half  the  waters  of  the  earth 
to  vibrate  with  wave  motion.  On  neighboring  shores  these 
waves  rolled  to  heights  of  60  or  70  feet. 

249.  Tides. — If  we  stand  on  the  shore  of  the  open  sea  we 
shall  observe  a  regular  rise  and  fall  of  the  waters,  even  in 
a  time  of  calm.  If  the  surface  be  at  its  highest  level  now, 
about  six  hours  later  it  will  be  at  its  lowest.  In  case  the 
shore  is  rocky,  the  boulders   and   cliffs   up  to  a  certain 


Fig.  198.— Low  tide  on  a  shelving  coast.    The  edge  of  the  water  is  now  far  away  and 
the  boats  are  stranded.    When  high  tide  returns  they  will  again  float. 

height  will  then  be  seen  covered  with  barnacles  and  drip- 
ping seaweeds.  Pools  left  by  the  receding  waters  will  be 
full  of  small,  shelled  creatures,  and  a  strand  several  rods, 
or  even  miles,  in  width  may  be  left  bare.  In  another  six 
hours  the  waters  will  have  crept  slowly  in  again  until  the 
upper  line  of  seaweeds  is  reached.  The  average  interval 
between  two  periods  of  High  Tide  is  twelve  hours  and 


THE  OCEAN  291 

twenty-five  minutes.  The  alternating  extremes  mark  Low 
Tide. 

About  the  shores  of  islands  the  rise  and  fall  are  small, 
often  not  more  than  2  or  3  feet.  On  the  borders  of  conti- 
nents the  change  is  greater.  Toward  the  head  of  a  long 
bay  which  has  an  open  mouth  and  narrows  gradually  the 
rise  and  fall  may  be  50  feet,  or  even  more.  The  Bay  of 
Fundy  and  the  estuary  of  the  Severn  fulfil  these  conditions, 
and  are  noted  for  their  great  tides.  On  open  shores  the 
water  falls  back,  or  creeps  up,  gently.  But  in  and  out  of 
these  landlocked  arms  it  goes  with  a  rush.  An  abrupt 
tidal  wave  with  a  steep  and  foaming  front  enters  some 
rivers,  as  the  Seine.  Such  a  wave  is  called  a  Bore.  High 
and  low  tides  do  not  always  occur  at  the  same  time  on 
opposite  sides  of  a  strait,  and  the  difference  in  level  causes 
a  swift  current,  known  as  a  Tidal  Eace.  Hell  Gate,  near 
New  York,  affords  an  illustration.  In  a  landlocked  sea 
which  has  a  very  narrow  entrance  from  the  ocean,  the  tides 
are  unimportant.  Those  of  the  eastern  shores  of  the  Med- 
iterranean Sea  are  scarcely  perceptible. 

The  tides  exist,  but  can  not  be  seen,  in  the  open  ocean. 
They  are  broad,  gentle  swells,  which,  like  wind  waves,  pile 
up  and  become  visible  at  the  shore.  If  the  earth  were 
covered  by  a  universal  ocean,  the  tidal  waves  would  for- 
ever roll  around  it  unseen.  But  the  lands  bring  them  to 
view. 

250.  What  is  the  cause  of  the  tides  ? — What  can  make  a 
wave  come  to  its  height  every  twelve  hours  and  twenty-five 
minutes  ?  Twice  this  period,  or  twenty-four  hours  and  fifty 
minutes,  is  the  time  from  one  setting  of  the  moon  to  the 
next,  and  this  fact  long  ago  led  people  to  connect  the  tides 
with  the  moon.  But  many  centuries  passed  before  the  re- 
lation was  wholly  understood.  The  full  explanation  would 
take  so  much  space  that  we  must  content  ourselves  with  a 
simpler  statement.  Suppose  a  man  and  a  boy  to  join  hands 
and  whirl  about.    Each  will  move  in  a  circle,  but  the  boy's 


292    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

circle  will  be  larger  than  the  man's  because  he  is  not  so 
heavy.  Each  will  feel  a  pull  in  his  arms,  and  they  must 
hold  fast  or  they  will  break  apart.  The  moon  and  earth 
whirl  about  in  a  similar  way,  making  one  turn  a  month,  but 
as  the  earth  is  eighty  times  the  heavier,  the  center  about 
which  they  circle  is  close  to  the  center  of  the  earth.  It  is 
in  fact  inside  the  circumference  of  the  earth.  Instead  of 
clasping  hands  they  are  held  together  by  Gravitation,  the 
same  attractive  force  which  keeps  us  from  being  whirled  off 
by  the  daily  rotation  of  the  earth.  The  earth  attracts  the 
moon  and  the  moon  attracts  the  earth.  Thus  the  earth 
feels  two  forces — an  attraction  or  pulling  toward  the  moon, 
and  a  pulling  away  from  the  moon  in  consequence  of  the 
circling.  The  pulling  away  is  called  the  Centrifugal  Force. 
To  make  this  quite  clear  let  us  look  at  Fig.  199.  C  is 
the  center  of  the  earth,  and  the  circle  about  it  is  the 
equator.     A  is  the  point  about  which  the  moon  and  earth 

circle.      The  centrifu- 
gal force  is  the   same 
/-N      for   all    parts    of    the 


Moon  earth,  but  the  attrac- 
tive force  is  not.  The 
principle  is  that  attrac- 

FiG.  199.— Diagram  to  illustrate  the  tides.     The      ^j^j^      |g     gtronffer     for 
shaded  belt  represents  the  ocean,  as  though  ^ 

a  complete  envelope.  Small    distances    than 

for  large,  and  under 
this  principle  the  moon  draws  the  nearer  side  of  the  earth 
more  than  it  does  the  farther  side.  At  D  and  E  the  moon's 
attraction  is  just  as  strong  as  the  centrifugal  force,  but 
nowhere  else  about  the  equator.  At  F  the  attractive  force 
is  greater  than  the  centrifugal,  and  the  difference  is  a  pull 
toward  the  moon.  At  G  the  centrifugal  force  is  greater 
than  the  attractive,  and  the  difference  pulls  away  from  the 
moon.  So  there  is  a  tendency  to  stretch  the  earth  out, 
making  the  diameter  G  F  greater  than  D  E.  The  water 
of  the  ocean  yields  to  these  pulls  and  is  drawn  together 


THE  OCEAN 


293 


and  piled  up  a  little  about  F  and  G.  These  two  swellings 
of  the  water  (greatly  exaggerated  in  the  diagram)  are  tidal 
waves. 

Up  to  this  point  we  have  paid  no  attention  to  the  fact 
that  the  earth  turns  once  in  twenty-four  hours  about  its 
own  center,  G.  The  effect  of  this  turning  is  to  carry  the 
tidal   waves   all   about 


the  earth's  circumfer- 
ence each  day,  and  as 
there  are  two  of  the 
waves,  each  part  of  the 
ocean  feels  two  high 
tides  and  two  low  tides. 
Thus  the  tides  are 
caused  by  a  combina- 
tion of  the  moon's  at- 
traction with  the  mo- 
tions of  the  earth. 

The  continents  and 
islands  and  the  shapes 
of  coasts  and  shoals  in- 
terfere with  the  free 
movements  of  the  wa- 
ters, but  in  each  ocean 
the  water  is  swayed 
twice  a  day,  and  from 
the  oceans  tidal  waves 
advance  against  the  coasts,  and  enter  all  the  bays.  Their 
speed  is  checked  as  they  enter  shallow  water,  and  their 
arrival  at  the  heads  of  long  bays  may  even  be  delayed  many 
hours.  For  the  guidance  of  shipmasters,  maps  are  made 
showing  by  "cotidal"  lines  (Fig.  200)  the  places  which  are 
reached  by  the  tides  at  the  same  time.  There  are  also 
tide-tables  for  all  ports,  to  tell  the  mariner  when  high  and 
low  tide  occur,  and  the  amount  of  rise  and  fall.  Many 
channels  can  be  used  at  high  tide  which  can  not  be  passed 


Fig.  200.— Cotidal  lines  in  and  near  Delaware 
Bay.  On  the  day  of  full  moon  or  new  moon 
high  tide  reaches  Cape  May  at  one  o'clock, 
Wilmington  at  half-past  four,  and  Philadel- 
phia between  six  and  seven.  Scale  of  map, 
1  inch  =  55  miles. 


294    AN  INTRODUCTION  TO   PHYSICAL   GEOGRAPHY 

at  any  other  time,  hence  the  knowledge  of  them  is  of  much 
practical  importance. 

251.  Ocean  currents. —  When  waves  started  by  winds, 
earthquakes,  or  tidal  attraction  traverse  the  ocean,  the 
water  itself  moves  little  except  in  shallow  or  confined  areas. 
We  are  now  to  study  movements  of  the  sea  in  which  there 
is  a  continual  transfer  of  water  for  long  distances. 

We  take  first  the  Gulf  Stream  and  the  ^orth  Atlantic 
Drift  (Fig.  201).  The  term  Gulf  Stream  is  properly  applied 
to  a  stream  of  salt  water  which  pours  eastward  from  the 
Gulf  of  Mexico,  between  Florida  and  Cuba,  and  then  bears 
northeastward  into  the  Atlantic.  The  width  of  this  current 
in  the  Florida  Straits  is  about  50  miles,  its  velocity  is  about 
50  miles  per  day,  and  it  is  several  hundred  feet  deep.  It  is 
very  warm  and  it  passes  between  "  walls  "  of  colder  water. 
As  the  stream  progresses,  its  waters  scatter,  their  velocity 
drops  to  a  few  miles  per  day,  and  thus  as  a  "  Drift "  they 
cross  the  middle  Atlantic  and  wash  the  shores  of  western 
Europe.  It  is  hardly  correct  to  say,  therefore,  that  the 
Gulf  Stream  touches  Europe  or  gives  it  a  mild  climate.  It 
is  true,  however,  that  the  neighboring  waters  are  warmed 
by  the  drift  from  the  tropics,  and  the  mild  winds  carry 
heat  and  moisture  from  the  sea  over  the  lands  of  western 
Europe. 

But  the  currents  of  the  K"orth  Atlantic  have  now  been 
described  only  in  part.  Flowing  westward  along  the  equa- 
tor is  a  strong  current,  some  of  which  passes  South 
America,  enters  the  Caribbean  Sea,  and  then  the  Gulf  of 
Mexico,  to  pass  out  as  the  Gulf  Stream.  Other  strands  of 
the  equatorial  current  turn  north  outside  of  the  West 
Indies  and  join  the  Gulf  Stream  waters  to  form  the  drift 
above  described.  At  the  far  northeast  some  of  the  waters 
push  on  into  the  arctic  seas,  and  others  return  southward 
along  the  shores  of  southwestern  Europe  and  western 
Africa,  and  pass  again  into  the  equatorial  current  moving 
west.     There  is  thus  a  complete  eddy  in  the  Korth  Atlan- 


Fig.  201.— Currents  of  the  Atlantic  Ocean.    The  arrows  show  direction.    The  heavy 
lines  are  the  courses  of  two  derelicts,  drifted  by  currents  and  winds. 

^95 


296    AN  INTRODUCTION  TO   PHYSICAL  GEOGRAPHY 

tic,  the  waters  moving  as  the  hands  of  a  watch.  In  the 
center  is  a  quiet  region,  where  vast  fields  of  seaweed  float, 
known  as  the  Sargasso  Sea. 

Beyond  Florida  the  Gulf  Stream  soon  bears  away  from 
the  shores  of  the  United  States,  which  are  washed  by  colder 
waters  from  the  north.  These  come  down  from  the 
neighborhood  of  Greenland  and  meet  the  Gulf  Stream  in 
what  is  known  as  the  "  cold  wall."  Along  this  belt  are  the 
Banks  of  Newfoundland,  and  here  the  contact  of  cooler 
with  warm,  moist  air  causes  dangerous  fogs. 

There  is  a  similar  eddy  in  the  South  Atlantic.  A 
division  of  the  equatorial  current  turns  southwestward 
down  the  coast  of  South  America,  and  returns  eastward 
to  Africa,  and  northward,  completing  the  circuit.  At  the 
south  the  easterly  flowing  current  mingles  with  a  great  drift 
passing  easterly  around  the  world  in  the  southern  seas. 
This  South  Atlantic  eddy  whirls  in  a  direction  opposite 
to  that  of  the  hands  of  a  watch. 

It  may  now  be  asked :  How  are  these  currents  known 
to  exist  ?  The  answer  is,  by  the  course  taken  by  drifting 
objects.  Certain  floating  but  abandoned  ships,  known  as 
derelicts,  are  now  and  then  sighted  by  vessels,  and  by  com- 
paring successive  positions,  their  course  can  be  plotted 
(see  Fig.  201).  Whenever  a  derelict  is  seen,  its  latitude 
and  longitude  are  reported  as  soon  as  possible  to  the 
United  States  Hydrographic  Office,  for  the  better  mapping 
and  safer  navigation  of  the  sea.  Thousands  of  sealed  bot- 
tles are,  from  time  to  time,  cast  into  the  sea.  They  con- 
tain, often  upon  blanks  furnished  by  the  Hydrographic 
Office,  record  of  the  latitude  and  longitude  at  which  they 
were  committed  to  the  waters,  with  a  request  that  the  finder 
transmit  to  Washington  the  point  of  their  coming  ashore. 
Less  than  in  former  days  is  the  sea  a  trackless  waste. 

In  the  Pacific  the  swing  is  more  vast,  but  the  general 
arrangement  of  eddies  is  similar  to  that  of  the  Atlantic, 
and  the  Japan  Current  resembles  the  Gulf  Stream.     The 


THE  OCEAN 


northern  eddies  of  both  oceans  are  more  perfect,  because 
formed  in  more  fully  enclosed  waters. 

The  currents  are  formed  by  the  winds.  This  is  seen  on 
a  small  scale  by  watching  the  floating  twig  in  the  pond, 
and  is  understood  for  the  oceans  by  studying  the  winds 
and  currents  together.  The  student  should  compare  the 
winds  of  the  Atlantic  (Fig.  180)  with  the  currents  of  the 
Atlantic  (Fig.  201).  The  great  current-makers  are  the 
steady  trade-winds,  driving  the  waters  westward  in  the 
tropics ;  the  prevailing  westerlies  of  middle  latitudes  drift 
them  eastward,  and  thus  the  great  eddies  are  maintained. 

252.  Ice  in  the  sea. — Icebergs,  singly  or  in  fleets,  leave 
the  shores  of  Greenland  in  the  spring  and  descend  far 
enough  into  the  Atlan- 
tic to  endanger  ships 
in  the  great  path  be- 
tween America  and 
Europe.  The  icebergs 
are  the  frontal  parts 
of  Greenland  glaciers 
which  have  pushed  into 
the  sea  far  enough  to 
float.  All  northern  seas 
are  more  or  less  crowded 
with  pack  or  floe  ice, 
formed  by  the  freezing 
of  the  surface  waters, 
and  moved  about  by 
winds  and  currents.  Po- 
lar exploration  abounds 
in  experiences  with 
such  ice.  Ships  are 
caught  and  crushed  in 
it.  Long  sledge -jour- 
neys are  made  over  it.  Through  it  Hansen  drove  the 
Fram,  and  over  it  he  made  his  final  dash  toward  the  pole. 


Fig.  202.— Floe  ice.  near  the  west  coast  of  Green- 
land. Great  cakes,  crushing  together,  are 
made  huminocky  at  their  edges. 


298    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

On  floe  ice  about  twenty  persons  of  the  Polaris  party 
drifted  south  for  2,000  miles  in  the  winter  of  1872-'73,  and 
were  picked  up,  after  a  journey  of  six  months,  off  southern 
Labrador.  Large,  flat-topped  icebergs  break  from  the  ant- 
arctic ice-fields  and  invade  the  South  Atlantic  and  South 
Pacific  Oceans. 

253.  Exploration  of  the  ocean.— This  has  been  done  in 
many  ways.     In  ancient  times  daring  mariners  in  small 


Fig.  203.— To  carry  the  sounding  wire 
to  great  depths  a  heavy  weight  is 
needed.  It  can  not  be  drawn  up 
again,  and  is  therefore  so  arranged 
as  to  disconnect  itself  at  the  bottom. 


Fig.  204. — A  deep-sea  dredge.  The  iron 
lip  of  the  sack  scrapes  shells,  mud, 
etc.,  into  it,  and  small  animals  are 
caught  by  the  "tangles." 


ships  learned  to  track  the  wastes  of  the  Mediterranean. 
Then  they  sailed  by  the  Pillars  of  Hercules  and  began  to 
creep  up  and  down  the  Atlantic  shores.  Hardy  vikings 
of  the  north  found  Iceland,  settled  in  Greenland,  and,  as 
many  believe,  followed  our  shores  as  far  as  New  England. 
Then  came   Columbus,   Magellan,   Drake,  Hawkins,  and 


THE  OCEAN  299 

Cook,  crossing  the  great  oceans  and  beginning  to  sail 
around  the  world.  In  our  modern  days  commerce  has 
threaded  all  waters,  daring  explorers  have  pushed  far  into 
the  frozen  north,  and  ships  have  gone  forth,  equipped  with 
apparatus  and  directed  by  men  of  science,  to  seek  the  mys- 
teries of  the  ocean.  The  forms  of  the  shores,  the  currents, 
the  temperature,  composition,  and  depth  of  the  water,  the 
life  of  the  upper  and  deep  waters — all  these  are  subjects 
of  study.  Sounding-lines,  dredges  for  bringing  muds  from 
the  bottom,  and  self-registering  thermometers  for  testing 
temperatures  at  the  bottom,  are  parts  of  the  apparatus  used. 
The  United  States  Coast  Survey  has  furnished  us  with 
much  of  our  knowledge  of  the  Atlantic  Ocean. 

254.  Life  of  the  ocean. — The  highest  forms  of  life  are 
on  the  land.  There  they  find  abundant  supplies  of  air,  and 
are  able  to  live  an  active  life.  Even  the  beasts  have  more 
elaborate  bodies  and  far  more  intelligence  than  the  highest 
creatures  that  live  in  the  sea.  But  all  land  creatures  are 
close  to  the  surface,  while  the  ocean  is  rich  in  living  crea- 
tures not  only  near  the  shore  and  at  the  surface  in  mid- 
ocean,  but  at  the  greatest  depths.  Vast  numbers  of  sea 
animals  have  delicate,  jelly-like  bodies,  made  almost  entirely 
of  water,  and  able  to  exist  only  in  water.  Others,  equally 
confined  to  a  watery  home,  have  hard  skeletons,  either  in- 
ternal, like  the  fishes,  or  on  the  outside,  like  the  crab,  the 
lobster,  and  the  innumerable  creatures  which  form  shells 
as  a  cover  for  their  bodies.  More  will  be  said  of  sea  ani- 
mals in  the  chapter  on  life. 

255.  Deposits  in  the  ocean.— We  have  seen  that  rivers 
may  enter  the  sea  and  build  out  the  land,  as  their  deltas 
grow.  But  not  all  the  waste  of  the  continents  is  dropped 
at  the  water's  edge.  The  finer  mud  floats  for  a  long  time, 
and  finally  settles  to  the  bottom  far  from  the  river  mouth. 
Thus  the  continental  shelves,  and  even  deeper  waters  out- 
side, receive  a  cover  of  muds  derived  from  the  land.  The 
shallow  waters  teem  with  fishes  and  shell  creatures,  and  at 


300    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


death  their  remains  mingle  with  the  muds.  Far  out,  how- 
ever, the  fine  muds  from  the  land  do  not  go.  But  multi- 
tudes of  minute  shells 
are  formed  by  creatures 
in  the  surface  waters. 
These  shells,  chiefly 
made  of  calcium  carbon- 
ate, sink,  when  the  ani- 
mals die,  to  the  deep 
sea-bottoms.  They  make 
a  fine  chalky  ooze  (Fig. 
205),  which  has  been 
brought  up  by  the  dredge 
and  studied.  In  the  very 
deepest  seas  a  fine  red 
clay  is  found.  This 
comes,  in  part  at  least, 
from  volcanic  dust,  which 
falls  on  all  seas.  The 
fine  deposits  of  mid- 
ocean  accumulate  very 
slowly,  while  the  muds 
of  offshore  waters  gather 
rapidly. 
256.  Navigation. — The  ocean  is  the  highway  of  nations. 
In  primitive  times  the  winds  furnished  power  and  the  sun 
and  stars  guided  the  course.  Now  the  mariner  has  a  charted 
sea ;  with  his  compass  on  the  deck  and  engines  in  the  hold, 
he  crosses  the  waters  whither  he  will,  and  his  speed  is 
scarcely  checked  even  by  waves  and  winds.  Storms  bring 
little  danger  to  the  great  steamship,  and  collision  and  fire 
are  so  well  avoided  that  travel  is  nearly  as  safe  on  the  ocean 
as  on  the  land.  Even  the  waves  are  robbed  of  their  fierce- 
ness by  allowing  a  little  oil  to  drip  from  the  prow,  and  a 
ship  with  its  hundreds  or  thousands  of  temporary  inhab- 
itants, and  with  all  provision  for  human  comfort,  seems 


Fig.  205.— a  deep -sea  deposit  composed 
shells.     Magnified  20  times. 


THE  OCEAN  301 

less  a  vehicle  than  a  floating  town.  The  Pacific  is  coming 
to  be  a  busy  highway  like  the  Atlantic,  and  the  building 
of  a  ship  canal  in  Central  America  will  make  possible  in 
the  tropical  regions  continuous  voyaging  around  the  world. 
Almost  equally  with  the  land,  is  the  sea  a  field  of  discovery, 
of  travel,  of  commerce,  and,  unhappily,  also  of  war. 

257.  Submarine  cables. — During  the  last  half  of  the  nine- 
teenth century  many  lines  of  telegraphic  communication 
have  been  stretched  between  Europe  and  America,  and  im- 
portant foreign  news  passing  between  civilized  lands  is 
rarely  one  day  old.  The  coming  years  will  see  an  equal 
development  of  marine  telegraphy  in  the  regions  of  the 
Pacific,  and  messages  without  wires  may  yet  place  all  ships 
in  constant  communication  with  the  land. 

258.  Fishing. — The  seas  are  an  important  source  of  sup- 
ply for  man.  The  shallow  waters  near  the  shore  teem  with 
fish  and  other  marine  animals  fit  for  food.  Hence  fishing 
communities  abound  on  the  shore,  like  Gloucester  in  Mas- 
sachusetts and  the  Marblehead  of  former  days.  From  the 
beginnings  of  voyaging  to  America,  fishing  has  been  carried 
on  over  the  Banks  of  Newfoundland,  and  the  French,  the 
English,  and  the  American  have  regarded  these  ocean  fields 
as  of  national  importance. 


CHAPTEE  XIY 

THE   MEETESTG   OF   THE   LAND  AND   SEA 

The  line  along  which  the  ocean  waters  wash  the  edge 
of  the  land  is  often  called  the  Shore,  or  Shore-Line ;  or 
we  may  use  the  term  Coast,  or  Coast-Line.  The  latter  sug- 
gests more  particularly  the  margin  of  the  land,  the  former 
the  border  of  the  sea.  We  have  deferred  our  study  of  this 
narrow  belt,  that  the  chapters  on  the  ocean  and  the  land 
might  prepare  us  to  understand  it.  We  have  already  learned 
some  facts  about  sea-borders,  as  in  connection  with  deltas 
(Sec.  42),  coastal  plains  (Sec.  150),  and  tidal  bays  (Sees. 
249  and  250).  We  shall  now  look  at  the  shore-lines  of  the 
United  States,  to  see  what  general  principles  we  can  gather 
from  them. 

259.  Shore-line  of  Maine. — This  will  be  understood  by 
reference  to  the  map  (Fig.  206).  Many  rocky  ridges  run 
in  a  southerly  direction  from  the  mainland  into  the  sea. 
Between  them  deep  bays  penetrate  the  land.  The  head- 
lands are  exposed  to  the  full  force  of  the  waves,  hence  no 
sands  or  gravels  can  lodge,  or  beaches  form  about  them. 
At  the  head  of  the  inlets,  however,  the  sands  and  clays, 
whether  brought  down  by  streams  or  swept  in  by  waves, 
may  lodge  and  form  floors  of  worn  waste,  to  which  the 
name  Beach  is  given.  The  south  parts  of  these  ridges 
are  often  surrounded  by  water,  forming  hundreds  of  islands 
fringing  the  shore.  The  shore-line  is  vastly  lengthened  by 
its  irregularity.  Calais  is  about  200  miles  from  Portland? 
but  the  shore-lines  between  the  two  places  are  said  to  be 
more  than  2,000  miles  long.  The  Penobscot  and  Kennebec 
302 


THE  MEETING  OF  THE  LAND  AND  SEA 


303 


enter  the  sea  through  deep  tidal  channels.  These  furrows, 
cut  in  the  edge  of  the  land  and  entered  by  the  sea,  are 
known  as  Fiords,  and  have  their  best  examples  along  the 
shores  of  Norway  and  Scotland.  They  were  begun  by 
rivers  and  finished 
by  glaciers  during 
the  Glacial  period. 

260.  Shore -line 
of  Massachusetts. — 
North  of  Cape  Ann 
are  the  smooth,  sandy 
beaches  known  as 
Salisbury  Beach  and 
Plum  Island,  with 
swamps  and  slug- 
gish tidal  streams 
behind  them  on  the 
west.  Cape  Ann  is 
a  rough,  rocky  head- 
land, enclosing  on 
the  south  the  quiet 
waters  of  Glouces- 
ter Harbor.  The 
waves  beat  upon  the 
granite  shore,  the 
coast-line  is  jagged, 
and  few  sands  can 
rest  about  its  ex- 
posed border.  To- 
ward Boston  the  wash  of  shore  currents  has  built  a  bar 
from  the  mainland  to  the  rocks  of  Nahant,  hence  Nahant 
is  an  old  island  tied  to  the  shore  by  a  recently  made  beach. 
The  same  is  true  of  Marblehead  Neck  ;  a  rugged  island 
is  bound  to  the  mainland  by  a  narrow  belt  of  sand  cast  up 
by  the  waves.  The  hills  in  Boston  Harbor  are  drumlins 
(Sec.  136)  and  show  many  shore  cliffs,  due  to  their  outer 
21 


Fig.  206.— Outline  of  part  of  the  coast  of  Maine. 
Scale,  1  inch  =  5^  miles.  The  sea  laps  against  a 
surface  shaped  by  glaciers,  converting  ridges  to 
promontories  and  islands,  and  making  bays  and 
straits  in  the  hollows. 


304    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

slopes  being  cut  away  by  wave  action.  At  Kantasket  is 
a  long,  smooth  beach  of  fine  sand,  a  little  concave  toward 
the  sea,  protecting  Hingham  Bay  to  the  westward.  These 
are  local  cases,  but  instructive,  and  should  be  studied 
upon  the  atlas  sheets  of  eastern  Massachusetts.  Nahant  is 
shown  in  Fig.  207.  Cape  Cod  has  a  very  smooth  eastern 
shore,  facing  the  ocean.  Low,  sandy  lands  formerly  ex- 
tended farther  east,  but  have  been  carved  away  by  the 
unceasing  attacks  of  the  waves.  Some  of  the  material  has 
been  swept  northward  by  currents,  carried  around  the  point, 
and  built  into  the  hook  which  encloses  Provincetown  Har- 
bor. We  should  note  the  difference  between  the  jagged 
shore  maintained  by  the  hard  rocks  of  Maine  and  the 
smooth  shore  carved  from  the  soft  beds  of  Cape  Cod.  We 
should  compare  also  the  rough,  irregular  shore-line  about 
the  protected  waters  of  Buzzards  Bay.  Kan  tucket  and 
Marthas  Vineyard  consist  wholly  of  soft,  easily  destroyed 
beds,  and  are  much  exposed  to  attacks  of  the  sea.  Hence 
the  shores  have  smoothly  curved  forms.  Bars  have  often 
been  carried  across  the  openings  of  bays,  turning  them  into 
lakes.  The  shores  of  Rhode  Island  and  Connecticut  are 
like  those  of  Maine.  The  rocks  are  ancient  and  hard,  and 
the  rivers  enter  great  bays  like  the  Narragansett,  or  pour 
through  narrower,  but  deep,  tidal  channels,  as  the  Thames 
from  Norwich  to  the  Sound. 

261.  New  York  and  New  Jersey. — The  most  important 
feature  of  the  Xew  York  shore-line  is  the  trough  of  the 
Hudson  River,  cut  many  feet  below  sea-level,  and  admitting 
the  tides  far  within  the  land.  Salt  water  reaches  Pough- 
keepsie,  and  the  rise  of  the  tides  is  felt  at  Albany  and 
Troy,  150  miles  inland.  Other  submerged  channels  are 
occupied  by  East  River,  Raritan  Bay,  the  Upper  Bay,  and 
the  Narrows,  affording  the  best  harbor  facilities  in  America. 
Outside  of  the  Lower  Bay  are  long  stretches  of  flat,  sandy 
beach,  made  by  waves,  and  by  currents  moving  along  the 
shore.     These  are  common  on  the  south  shore  of  Long 


Fig.  207. — Part  of  the  coast  of  Massachusetts.  Scale,  1  inch  =  1  mile.  Contour  in- 
terval, 20  feet.  Nahant  and  Little  Nahant,  originally  islands,  have  been  joined 
together  and  to  the  mainland  by  spits. 


O-     THE 

UNIVlkoIT 


T'^fxrw^'-n^w^' 


Fig.  208— New  York  and  vicinity,  showing  the  harbor  and  its  approaches.    Scale, 
1  inch  =  9  miles.    (See  pages  304  and  315.)    Copyrighted  by  E.  E.  Howell. 

305 


306    AN   INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


rnegat  Inlet 


Fig.  209.— The  coast  of  New  Jersey,  showing 
wave-made  spits  and  barriers,  and  quiet 
waters  behind.    Scale,  1  inch  =  11  miles. 


Island.  Rockaway  and 
Coney  Island  Beaches 
run  out  to  points  on  the 
west  (Fig.  208),  and  were 
made  by  shore  currents 
driven  by  winds  from  the 
east.  Behind  them  are 
Gravesend  and  Jamaica 
Bays  and  a  network  of 
swamps  and  channels. 

If  we  turn  to  the  New 
Jersey  shore  we  find 
Sandy  Hook  stretching 
up  into  the  Lower  Bay 
(Fig.  209),  built  by  cur- 
rents moving  north  along 
the  Jersey  shore.  Far- 
ther south  are  low  bluffs, 
due  to  cutting  back  by 
the  waves.  This  is  the 
quarry  to  supply  the  sea 
with  sand  for  the  build- 
ing of  Sandy  Hook. 
From  Point  Pleasant  to 
Cape  May  is  a  nearly 
unbroken  beach,  long, 
narrow,  low,  and  sandy, 
with  a  belt  of  quiet  water 
separating  it  from  the 
mainland.  The  waves 
there  break  in  shallow 
water,  drop  the  load  of 
waste  they  have  pushed 
in  from  the  sea-bottom 
just  outside,  and  form 
thus  an  offshore  beach. 


THE  MEETING  OF  THE  LAND  AND  SEA  307 

Here,  as  along  other  parts  of  the  Atlantic  coast,  a  canoe 
could  sail  in  quiet  waters  for  long  distances. 

262.  The  South  Atlantic  and  Gulf  coasts.— Here  we  have 
long  lines  of  straight  or  gently  curved  shore,  with  shallow 
sea-bottoms  and  low,  flat  lands.  Great  bays  or  smaller  in- 
lets often  break  this  smooth  line.  Such  are  the  Delaware 
and  Chesapeake  Bays,  Albemarle  and  Pamlico  Sounds,  Pen- 
sacola  and  Mobile  Bays.  All  the  larger  rivers  of  Virginia 
and  Maryland  discharge  into  the  Chesapeake  Bay,  and 
from  the  bay  the  tide  flows  far  up  the  streams.  Hence  we 
have  the  expressive  name  "  Tide-water  Virginia,"  because 
all  the  low  plains  of  the  State  are  threaded  by  tidal  rivers. 
As  we  go  southward,  long  offshore  beaches  and  fringes  of 
islands  border  the  Carolinas  and  much  of  Florida.  Texas 
shows  a  wonderful  extent  of  these  low,  long,  and  sandy  off- 
shore beaches.  Nearly  the  entire  Texas  coast  for  300  miles 
has  such  a  shore-line,  running  in  a  smooth,  gentle  curve, 
with  lagoons  and  bays  behind.  Galveston  is  on  such  a 
beach,  with  Galveston  Bay  behind  it,  and  was  thus  exposed 
to  fearful  destruction  by  storm  waves  when,  in  1901,  a 
West  India  hurricane  abandoned  the  ordinary  course  and 
turned  westward  across  the  Gulf. 

263.  The  Pacific  coast-line. — This  is  less  winding,  along 
the  western  border  of  the  United  States,  than  much  of  our 
eastern  shore-line.  Instead  of  low,  coastal  plains,  we  find 
cliffs  and  mountainous  elevations  rising  from  the  water. 
Barrier  beaches  are  few,  because  the  water  deepens  rapidly 
and  waves  break  at  the  very  edge  of  the  water,  instead  of 
offshore.  There  are  three  principal  breaks,  by  which  ocean 
waters  flow  within  the  land.  The  Golden  Gate  is  a  narrow 
channel  leading  into  a  system  of  bays  lying  behind  low 
mountains,  the  Columbia  Eiver  is  open  to  the  tides  for 
some  distance,  and  Puget  Sound  offers  an  extensive  system 
of  protected  sea-waters.  The  last  named  are  fiords  and  are 
the  beginning  of  a  great  system  extending  northward  along 
the  shores  of  British  Columbia  and  Alaska.    The  waters 


308    AN  INTRODUCTION   TO  PHYSICAL  GEOGRAPHY 

are  deep,  and  the  coast  is  fringed,  not  by  barrier  beaches, 
but  by  a  continuous  chain  of  mountaitious  islands,  behind 
which  protected  channels  of  coastwise  navigation  may  be 
found.     In  growing  rugged  at  the  north  our  west  coast  but 


Fig.  210.— The  fiords  of  northwestern  Washington.     Scale,  1  inch  -  38  miles      The 
sea  invades  hollows  shaped  by  ancient  glaciers. 

repeats  the  features  of  the  east  coast,  for  the  irregular 
shore-lines  of  New  England  pass  into  yet  more  broken  lines 
about  the  Canadian  provinces  and  the  Gulf  of  St.  Lawrence. 
264.  Summary  of  principles. — Having  learned  the  chief 
facts  about  the  coast-line  of  our  continent,  we  shall  now 


THE  MEETING  OF  THE  LAND  AND  SEA  309 

classify  and  more  fully  explain  them,  and  compare  with 
them  some  of  the  features  of  other  parts  of  the  world.  The 
behavior  of  the  water  where  it  washes  the  land,  is  much 
the  same  everywhere,  giving  us  the  same  kinds  of  coast 
forms.  Even  on  the  borders  of  pools  and  small  lakes  the 
student  may  find  in  miniature  what  the  ocean  displays  on 
a  scale  of  magnificence. 

265.  Wave  work. — We  have  already  learned  that  winds 
raise  waves,  that  waves  move  over  the  sea,  that  they  break 
against  the  edge  of  the  land,  and  send  the  water  rushing 
upon  it.  These  waves  attack  the  rocks  of  an  uneven  land 
border.  They  pick  up  pebbles  and  stones  and  hurl  them 
against  the  ledges  of  the  shore.  Grinding  away  the  lower 
ledges,  they  undermine  the  ledges  higher  up,  and  thus  form 
cliffs.  In  front  of  the  cliffs  nearly  flat  platforms  are  made, 
and  strewn  with  the  coarser  waste.  The  finer  mud,  easily 
washed  away,  is  floated  out,  to  settle  at  a  greater  or  less 
distance  from  the  land.  Waves  do  the  most  of  their  work 
at  the  level  of  the  sea.  Storm-waves  may  dash  a  hundred 
feet  or  more  above  it,  and  may  grind  strongly  over  shallow 
bottoms,  but  they  have  no  effect  on  the  deeper  bottoms. 
The  waves  act  as  a  saw,  cutting  horizontally  against  the 
edge  of  the  lands. 

266.  Beach  platforms. — Let  us  look  more  closely  at  the 
stretch  of  sand,  pebbles,  or  boulders  that  so  often  borders 
the  sea.  The  wave-saw  has  cut  a  notch  into  the  sloping 
land,  and  the  continual  moving  in  and  out  of  waves  and 
tides  strews  the  floor  with  the  waste  of  the  land.  This 
platform  slopes  gently  toward  and  under  the  water.  It 
may  be  covered  entirely  at  high  tide,  but  a  strip,  perhaps 
many  rods  wide,  is  bare  at  low  tide.  Sometimes  the  beach 
platform  is  a  floor  of  solid  rock.  This  means  that  waves, 
or  currents  moving  along  the  shore,  sweep  all  the  waste 
off  to  some  other  point. 

267.  Sea-cliffs. — Overlooking  the  beach,  if  the  sea  beats 
upon  the  edge  of  high  land,  is  a  cliff.     It  may  be  vertical 


310    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

and  rise  for  hundreds  of  feet,  as  at  some  points  on  the 
shores  of  Scotland  and  California.  It  may  even  overhang 
in  places,  if  the  rock  is  strong  enough  to  hold,  and  sea  cav- 
erns may  have  been  formed  underneath  by  the  dash  of  the 
surf,  ringal's  Cave  is  cut  200  feet  into  the  south  side  of 
the  island  of  Staffa,  off  the  Scottish  coast.  The  floor  of  the 
cave  is  below  the  sea  surface,  and  the  roof  is  50  or  more 
feet  above  it.     The  waves  rush  in  and  are  still  quarrying  out 


Fig.  211.— Cliffs  and  irregular  platform  wrought  from  hard  rock  by  sea-waves ; 
Nova  Scotia. 

the  great  columns  of  ancient  lava  that  compose  the  island. 
Where  the  border-land  is  not  solid  rock,  but  clay  or  sand, 
the  cliff  slopes  down  to  the  beach  more  gently,  as  seen  in 
Fig.  77.  At  Sankaty  Head,  Nantucket,  is  such  a  sloping 
cliff  cut  in  land  about  100  feet  high.  Such  are  the  Gay 
Head  cliffs  of  Marthas  Vineyard,  and  many  cliffs  in  the 
soft  beds  of  Norfolk  and  other  parts  of  the  east  English 
shore,  where  farms  and  village  sites  have  in  times  past 
been  cut  away  and  absorbed  by  the  North  Sea. 

268.  Lagoons  and  barrier  beaches. — We  have  seen  that 
these  are  common  on  our  Atlantic  and  Gulf  coasts.    They 


THE  MEETING  OF  THE  LAND  AND  SEA 


311 


belong  to  shore-lines  along  which  the  water  is  shallow  for 
some  distance  from  shore.  This  means  that  incoming 
storm-waves  break  at  some  distance  from  the  land,  and 
spend  their  force  there.  The  rush  of  the  surf  stirs  the 
waste  on  the  bot- 
tom, carries  it  for- 
ward a  little  way, 
and  then  drops  it. 
By  this  process  a 
low  ridge  is  raised 
from  the  bottom, 
is  built  at  length 
above  the  water, 
and  may  be  broad- 
ened by  the  addi- 
tion of  waste  against 
its  outer  slope.  The 
quiet  water  on  the 
land  side  is  known 
as  a  Lagoon.  It  re- 
ceives fresh  water  from  the  land,  and  tends  to  become 
brackish.  Muds  from  the  land  gather  in  lagoons,  and 
plants  grow  in  them,  and  they  are  gradually  filled. 

269.  Traveling  beaches  and  spits. — Often  the  same  wind 
which  makes  large  waves  will  cause  a  current  to  flow  along 
the  shore.  The  waste  lifted  by  each  wave  is  then  carried 
forward  a  little  by  the  current  before  it  drops  again  to  the 
bottom.  In  this  way  the  waste  slowly  travels  in  the  direc- 
tion of  the  current.  If  the  shore  is  straight  the  waste 
follows  it,  but  if  the  shore-line  bends  back  the  waste  keeps 
straight  on,  and  is  built  into  a  low  cape  or  spit  (Fig.  214). 
Sandy  Hook  is  a  spit  curved  at  the  end.  Sometimes  a  spit 
grows  all  the  way  across  a  bay  so  as  to  close  it,  and  some- 
times it  joins  an  island  to  the  mainland  (Fig.  207).  A 
barrier  usually  becomes  a  traveling  beach  also,  and  its  sand 
is  shifted  to  and  fro  as  the  shore  current  changes, 


Fig.  212. 


Barrier  and  lagoon  on  the  shore  of  Lake 
Ontario. 


Fig.  213.— a  traveling  beach  on  the  shore  of  Lake  Ontario.    The  stones,  originally 
angular,  become  rounded  as  the  waves  roll  them  along. 


i 


Fig.  214.— a  curved  spit,  made  by  waves,  on  the  shore  of  Xjake  Michigan. 


THE   MEETING  OF  THE  LAND  AND  SEA 


313 


270.  Irregular  shore-lines  tend  to  become  smooth. — Let  us 

take  the  Maine  shore  as  an  illustration.  Wherever  a  stream 
enters  the  head  of  a  bay  it  makes  a  delta  and  shallows  the 
water,  or  even  pushes  the  shore-line  forward.  At  the  same 
time  the  waves  cut  away  the  exposed  headlands,  and  while 
some  of  the  waste  from  this  cutting  goes  out  to  sea,  some 
of  the  sands  and  gravels 
are  often  swept  into  the 
bay,  and  form  within  it 
a  curved,  smooth  beach. 
This  curve  may  straight- 
en out  as  it  receives 
more  material,  and  so 
by  this  double  or  triple 
process  the  entire  shore- 
line will  grow  in  time 
to  be  smooth  and  uni- 
form. Where  the  head- 
lands are  of  soft  mate- 
rials, as  on  the  south 
shore  of  Marthas  Vine- 
yard, the  work  goes  on  rapidly,  the  spits  soon  become 
barriers,  and  the  bays  are  shut  off  from  the  sea  and  become 
lakes. 

271.  Coast-lines  of  rising  lands. — Consider  a  land  stand- 
ing at  a  given  height  in  relation  to  the  bordering  sea.  The 
waste  of  the  land  is  spread  smoothly  in  the  shallow  waters. 
If  the  land  rises,  these  plains  of  waste  become  flat  grounds 
on  the  edge  of  a  continent.  We  have  followed  such  changes 
in  our  study  of  marine  plains  (Sec.  150).  Such  a  coast-lin« 
is  smooth,  and  the  waters  deepen  very  gradually  from  their 
edge.  Hence  offshore  beaches  will  form.  These  are  the 
conditions  of  southern  New  Jersey  and  our  south  Atlantic 
coast. 

If  coasts  are  steep  and  the  seas  deepen  rapidly,  no 
marine  plain  is  uncovered  by  the  rising  of  the  land,  but  a 


Fig.  215.— Beach  at  the  head  of  Conception 
Bay,  Newfoundland.  The  waves  have  here 
made  the  shore-line  smooth. 


314    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

beach  platform  and  cliff  is  carried  above  the  sea  surface 
and  left  as  an  ancient  sea-margin  on  the  slopes  that  rise 
from  the  water  (Fig.  8).  Such  old  beaches,  or  marine  ter- 
races, are  found  on  the  coast  of  Maine  and  along  the  ocean 
borders  of  Alaska,  Cuba,  Norway,  and  Scotland. 

272.  Coast-line  of  sinking  lands. — This  subject  is  not 
altogether  new  to  us  (see  pages  64-65).  The  edge  of  any 
land  is  creased  by  streams,  and  thus  divided  into  a  series  of 
higher  grounds,  separated  by  valleys.  On  the  down-sinking 
of  the  land  the  sea  flows  into  these  valleys  and  "  drowns  " 
the  lower  part  of  the  rivers.  The  coast-line  thus  produced 
is  very  crooked,  and  there  are  often  many  islands.  The 
waves  and  currents  busy  themselves  with  the  work  of 
straightening,  and  in  time  the  water-front  shows  a  rapid 
succession  of  cliffs,  traveling  beaches,  and  spits. 

273.  Coast  swamps. — When  a  lagoon  forms  behind  a  bar- 
rier beach,  and  its  quiet  waters  become  so  shallow  that 
plants  grow,  we  have  a  coast  swamp.  Or  if  the  land  is 
sinking,  and  low,  flat  areas  are  flooded,  swamps  develop. 
In  either  case  the  tide  flows  in  and  out,  and  with  its  in- 
coming brings  mud,  which  settles  among  the  stems  of  the 
plants  and  raises  the  surface.  This  is  the  origin  of  the 
salt  meadows  whose  grasses  are  harvested  on  many  shores. 
Among  the  meadows  channels  form,  by  which  the  tidal 
waters  first  roll  in  and  last  drain  out.  By  building  dikes, 
hundreds  of  thousands  of  acres  yet  below  high  tide  are 
reclaimed  for  agriculture  and  for  homes.  This  saving  of 
rich  coastal  swamps  has  gone  on  most  extensively  in  Hol- 
land and  in  the  low  Fen  country  of  eastern  England.  The 
saving  of  these  lands  has  been  the  work  of  centuries,  and 
further  extensive  operations  are  now  in  hand  for  reclaim- 
ing the  Zuyder  Zee  in  Holland.  The  abundance  of  land  in 
America  has  thus  far  made  it  unnecessary  to  reclaim  much 
of  the  swamp  area  of  our  coasts. 

274.  Lake  shores. — In  Section  154  an  account  was  given 
of  a  large  lake  of  which  Great  Salt  Lake  is  the  remnant. 


THE  MEETING  OF  THE  LAND  AND  SEA  315 

Deeply  cut  shore-lines  are  found  at  various  levels  on  the 
surrounding  slopes,  up  to  1,000  feet  above  the  present  lake. 
These  shores  are  like  abandoned  beaches  of  the  ocean, 
except  that  they  have  been  left  high  and  dry  by  the 
gradual  drying  away  of  the  lake,  instead  of  by  the  rising  of 
the  land.  In  lakes  the  tides  are  unimportant.  Wind  waves 
do  their  work  on  ocean  and  lake  border  alike,  except  that 
most  lakes  are  so  small  that  the  waves  have  little  space 
in  which  to  develop,  and  are  therefore  small  and  weak. 
Still,  upon  lakes  less  than  a  half-mile  wide,  well-developed 
beaches  are  often  found,  and  a  succession  of  little  hori- 
zontal platforms  or  beaches  may  often  be  found  running 
about  a  pond  or  reservoir  whose  waters  have  been  from 
time  to  time  drawn  down.  At  each  stand  of  the  surface,  a 
new  shore-line  is  made.  Even  where  a  pool  has  dried  away 
by  the  roadside,  beaches,  deltas,  bars,  and  spits  may  often 
be  seen  (Fig.  40). 

275.  Harbors  and  cities. — The  waters  of  the  lower  Hud- 
son are  protected  from  the  ocean  waves  by  surrounding 
lands  (Fig.  208).  They  are  not  so  broad  that  the  winds  can 
stir  up  great  waves  upon  them.  They  are  deep  enough  for 
sea-going  vessels,  and  are  connected  by  a  deep  channel  with 
the  ocean.  Hence  they  form  a  harbor.  Boston  Harbor  is 
in  a  recess  of  the  shore-line  and  protected  by  many  islands. 
Philadelphia  lies  on  the  great  estuary  of  the  Delaware 
Eiver,  and  Baltimore  at  the  head  of  the  land-locked  Chesa- 
peake Bay.  Sinking  or  sunken  coasts  have  many  harbors, 
and  rising  coasts  have  few.  The  point  where  ships  can 
come  safely  to  the  land  is  the  natural  home  of  commerce. 
There  men  gather,  there  manufactured  products  are  made 
and  can  at  will  be  sent  seaward  or  landw^ard.  The  relation 
of  a  harbor  to  the  land  is  also  important.  The  supremacy 
of  New  York  is  due  in  part  to  the  easy  passage  from  its 
harbor  to  the  heart  of  the  continent.  The  navigable  Hud- 
son and  the  low  pass  by  the  Mohawk  Valley  through  the 
Appalachian  uplands  have  combined  with  its  good  harbor 


316    AN  INTRODUCTION   TO   PHYSICAL  GEOGRAPHY 


Fig.  216.— The  Golden  Gate.  Scale,  1  inch  =  40  miles. 
Except  at  this  point  the  Great  Valley  of  California 
is  separated  from  the  sea  by  a  mountain  barrier 
(see  Fig.  129).  Here  an  outlet  for  commerce  is 
combined  with  a  good  harbor. 

Japan,  China,  the  Philippines,  and 
Britain's  commercial 
greatness  has  grown  in 
part  from  her  drowned 
rivers  and  resulting  har- 
bors. She  has  no  river 
that  would  be  impor- 
tant if  not  tidal.  Lon- 
don, Bristol,  Liverpool, 
Southampton,  and  Glas- 
gow are  great  cities  be- 
cause of  the  sinking  of 
the  land.  But  not  all 
harbors  are  in  fiords  and 
drowned  valleys.  In 
the  lower  or  delta  chan- 
nels of  great  rivers,  as 
at  Xew  Orleans,  or  be- 
hind barriers,  or  hooked 
spits,   as    at    Province-    fig.  2i7.-0ut]ine 

town,     Mass.,     shipping  tion  of  its  great 

'  '  x-r      o  TiveTB  and  the 

may  find  a  haven.  isie  of  Wight. 


to  make  it  the  lead- 
ing port  of  the  At- 
lantic seaboard. 

Splendid  har- 
bors, too,  about  the 
Golden  Gate  (Fig. 
216)  and  Puget 
Sound  (Pig.  210) 
have  fixed  the  cen- 
ters of  life  on  the 
Pacific  coast,  be- 
cause thence  lead 
the  steamship  high- 
ways to  Hawaii, 
the   Indies.      Great 


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of  England,  showing  the  rela- 
commercial  cities  to  drowned 
drowned  valley  north  of  the 
Scale,  1  inch  =  250  miles. 


THE  MEETING  OE  THE  LAND  AND  SEA 


m 


276.  The  United  States  Coast  Survey.— Through  this  or- 
ganization our  Government  provides  minute  knowledge  of 
our  entire  shore-line.  Soundings  off  all  shores,  in  full  de- 
tail in  all  harbors  and  harbor  entrances,  and  with  frequent 
revision,  to  keep  pace  with  the  shifting  bottoms  of  the  bor- 
der seas — such  is  the  work  of  this  bureau,  that  charts  may 
be  issued  for  the  use  of  mariners  and  coast  dwellers.  A 
similar  survey  under  a  separate  bureau  is  carried  on  for 
the  Great  Lakes,  for  the  benefit  of  the  vast  shipping  inter- 
ests of  these  inland  waters. 

277.  Lighthouses  and  life-saving  stations. — The  light- 
house tells  the  sailor  both  where  to  go  and  where  not  to  go. 


Fig.  218.— a  life-saving  station  on  the  coast  of  Maine. 


On  the  Navesink  Highlands  of  eastern  New  Jersey  it  di- 
rects the  mariner  toward  the  harbor  of  New  York.  In  the 
English  Channel  beacon  lights  warn  the  sailor  off  the  Eddy- 
stone  rocks.  Such  lights  are  guides  to  all  vessels,  even 
those  that  cross  the  wide  seas.     Especially  needful  are  all 


318    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

possible  marks,  such  as  buoys  and  Hghts,  for  the  smaller 
vessels  engaged  in  coastwise  trade,  or  in  fishing.  Such 
craft  are  always  near  the  point  of  danger  and  in  risk  of 
running  upon  shoals  in  the  darkness  or  in  storms. 

Life-saving  stations  are  established  along  frequented 
shores,  with  every  appliance  for  aiding  distressed  mariners, 
and  maintaining  in  times  of  special  danger  a  watchful 
patrol  of  the  shore. 


CHAPTEK  XV 

LIFE 

We  have  looked  upon  the  Earth  as  a  whole.  We  have 
studied  its  lands,  its  atmosphere,  and  its  mantle  of  waters. 
We  come  now  to  the  living  things  which  throng  our  planet. 
They  are  animals  and  plants.  The  botanist  studies  the 
plants,  tells  us  their  structure,  their  habits,  how  they  are 
related  to  one  another,  and  how  they  divide  into  small  and 
great  groups.  Zoology  is  devoted  to  the  animal  kingdom 
and  gives  to  those  who  seek  it  the  same  full  knowledge  of 
these  forms.  But  geography  seeks  only  to  know  the  greater 
truths  about  living  things.  Plants  make  a  carpet  over  the 
lands — a  carpet  varying  according  to  climate  and  soil.  Ani- 
mals too  are  found  in  groups  over  the  world,  devouring 
plants  and  other  animals  for  food.  Living  things  covering 
the  land  and  swarming  in  the  seas,  and  seen  in  their  group- 
ing and  general  relations,  belong  to  geography. 

Plants  of  Koeth  Ameeica 

278.  Forests.— The  eastern  United  States  abounds  in 
forests,  while  the  West  is  forested  only  in  the  high  moun- 
tains and  along  part  of  the  Pacific  coast.  Trees  grow  in 
the  regions  best  supplied  with  water.  The  western  bound- 
ary of  the  eastern  forest  area  is  a  line  running  irregularly 
north  and  south  from  the  eastern  Dakotas  through  central 
Texas.  But  this  region  includes  the  prairies  of  Iowa,  Illinois, 
and  other  States,  where  forests  are  almost  confined  to  the 
water-courses.  The  great  forests  are  in  the  Great  Lakes 
region,  the  Appalachian  Mountains,  and  on  the  Gulf  Plains. 
22  319 


320    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


Chestnut,  oak,  maple,  beech,  walnut,  and  cherry  are  among 
the  hardwoods  of  the  East.  The  broad-leaved  trees  chiefly 
compose  these  Appalachian  forests  (Fig.  219),  often  number, 
ing  50  kinds  or  more,  while  the  narrow-leaved  or  coniferous 

trees  show  a  half-dozen 
sorts.  White  pine,  hem- 
lock, and  spruce  are 
common  in  New  Eng- 
land, in  Michigan,  and 
farther  west  along  the 
lakes.  Along  the  South 
Atlantic  and  Gulf 
plains  the  hard  pines 
flourish,  with  magno- 
lias, tulip,  gums,  and 
cypress. 

The  Great  Plains 
are  too  dry  for  trees 
except  here  and  there 
along  the  rivers.  Even 
the  lower  valleys  among 
the  Eocky  Mountains 
(Sec.  163)  are  without 
trees.  The  high  moun- 
tain valleys  and  slopes 
are  forested  up  to  the 
so-called  timber-line, 
the  trees  belting  the 
slopes  in  successive 
zones  controlled  by  tem- 
perature and  moisture. 
Next  the  bushy  low- 
lands are  low  junipers  and  nut-pines;  then,  in  order,  yel- 
low pines,  Douglas  firs  and  silver  firs,  with  occasional  groves 
of  aspen.  In  the  arid  belt  between  the  Eocky  Mountains 
and  the  Sierra  Nevada  most  mountains  do  not  reach  up- 


FiG.    219. —  An   Appalachian   forest  of  broad- 
leaved  (or  deciduous,  or  hardwood)  trees. 


LIFE 


321 


ward  to  timbep-line,  but  end  in  the  zones  of  juniper  or  yel- 
low pine.  On  the  Sierra  and  along  the  moist  North  Pacific 
region  all  cone-bearing  trees— pines,  firs,  hemlock,  cedars, 
and  sequoias — have  a  wonderful  development,  towering  to 
great  heights,  and  con- 
stituting the  most  mag- 
nificent forests  of  our 
continent  (Fig.  220). 

In  Canada  are  great 
forests.  Only  two  re- 
gions are  treeless.  One 
of  these  is  the  great  in- 
terior plain  continuing 
from  Dakota  and  Mon- 
tana northward.  The 
other  is  the  far  north- 
ern area,  called  "bar- 
ren grounds,"  which  is 
too  cold  for  forest 
growth.  Much  land  in 
the  southeastern  prov- 
inces has  been  cleared, 
but  enormous  forests 
stretch  from  the  Lau- 
rentian  uplands  to 
Hudson  Bay,  and  others 
from  the  basin  of  Mac- 
kenzie Eiver  southward 
along  the  slopes  and 
valleys  of  the  western 
mountains.  The  latter 
extend  over  Alaska  to 
the  Pacific  coast.  At  the  east  are  scrub  pine,  white  and  black 
spruce,  larch,  aspen,  and  birch.  At  the  west  are  spruces, 
firs,  hemlocks,  and  cedars.  The  softer  woods,  like  spruce, 
poplar,  and  basswood,  are  much  used  for  making  wood  pulp. 


Fig.  220.— a  pine  forest  of  the  Sierra  Nevada. 
Pines  are  narrow-leaved  (or  evergreen,  or 
cone-bearing)  trees. 


322    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

Southern  Mexico  and  Central  America  show  forests  of 
the  tropical   sort.     Palms,  rosewood,  mahogany,  logwood. 


Fig.  221.— a  tropical  forest,  Yucatan. 

and  rubber  trees  are  common,  while  upon  the  mountains 
more  northern  types,  such  as  oaks  and  pines,  are  found. 

279.  Forestry. — This  is  the  name  given  to  a  scientific 
system  of  managing  woodlands.  The  United  States  De- 
partment of  Agriculture  maintains  a  Bureau  of  Forestry, 
to  study  forest  problems  and  give  skilled  assistance  to  forest 


LIFE  323 

planters  and  owners.  In  the  early  days  the  settlers  cut  off 
forests  wastet'ully,  to  clear  the  land.  Now  it  has  become  a 
matter  of  public  interest  to  regulate  tree-cutting  and  to 
plant  forests.  This  is  done  in  part  to  keep  a  supply  of 
timber,  and  in  part  to  regulate  floods  and  prevent  the  waste- 
ful washing  of  the  soil.  The  cutting  of  the  Adirondack 
woods  exposes  the  spongy  cover  of  mosses  and  leaves  to 
destruction,  and  lets  the  storm-  and  snow-water  run  swiftly 
off,  flooding  the  Hudson,  while  at  other  times  the  water  is 
low  and  scanty.  In  other  words,  the  soil  mantle  and  its 
nap  of  vegetation  serve  as  a  reservoir  to  hold  the  water  and 
dole  it  out  throughout  the  year.  This  storage  service  and 
the  preservation  of  the  Adirondacks  as  a  playground  are 
regarded  as  so  important  that  the  State  is  purchasing  and 
reserving  much  forest  land  in  these  mountains.  Similarly, 
the  National  Government  is  reserving  forest  parks,  as  in 
the  Yellowstone  region  and  among  the  mountains  of  Cali- 
fornia. The  care  of  existing  forests  consists  mainly  in 
proper  thinning,  and  cutting  only  the  mature  timber,  instead 
of  reaping  a  wasteful  harvest  at  the  expense  of  the  future. 
Some  land  in  New  England,  no  longer  regarded  as  prof- 
itable under  the  plow,  is  relapsing  into  forest.  Schools  of 
forestry  are  being  established,  as  at  Cornell  and  Yale  Uni- 
versities, and  on  the  Biltmore  estate  in  North  Carolina. 

280.  Small  plants  in  forests. — In  the  moist  and  shaded 
places  beneath  forest  trees,  low  growths  flourish.  If  enough 
light  streams  in,  flowering  herbs  will  thrive,  as  in  our  north- 
ern woods,  and  in  any  case  mosses  and  other  lowly  plants 
will  establish  themselves.  Hence  we  may  think  of  these 
wild  grounds  as  having  several  layers  of  vegetation,  from 
the  modest  mosses  up  to  the  forest  monarchs. 

281.  Natural  meadows. — This  is  another  name  for  Prairies. 
The  student  should  review  Section  159.  There  the  origin 
of  the  plains  was  the  special  theme.  Here  we  refer  to  the 
vegetation.  Trees  are  absent  except  along  the  streams. 
Coarse  grasses  and  large  flowering  herbs  cover  the  ground 


324:  AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

in  its  natural  state.  The  glowing  colors  of  the  aster,  golden- 
rod,  and  other  tall  plants  are  common.  The  great  prairie 
region  separates  the  region  of  the  eastern  forest  from  the 
Great  Plains,  on  which  forests  do  not  grow  because  the 
climate  is  too  dry.  But  the  climate  of  the  prairies  is  not 
unfavorable  to  tree  growth.  The  tree  limit  has  been 
crowded  eastward  beyond  its  natural  position  by  fires.  Two 
centuries  ago  there  were  prairies  of  some  extent  in  central 
Virginia  and  western  ^ew  York,  but  their  boundaries  have 
disappeared  with  the  clearing  of  the  trees  from  the  sur- 
rounding lands. 

282.  Alpine  plants. — The  term  Alpine  is  derived  from 
the  lofty  mountains  of  southern  Europe,  but  applied  to  sim- 
ilar characters  and  conditions  wherever  found — to  scenery, 
climate,  plants,  animals,  and  even  the  customs  of  men.  In 
eastern  ^orth  America  most  of  the  mountains  are  too  low 
to  reproduce  Alpine  conditions  of  plant  life,  and  forests 
usually  rise  to  the  top.  But  in  the  western  mountains  are 
high  fields  and  slopes,  above  the  timber-line,  where  the 
ground  is  often  closely  covered  by  a  mat  of  low  plants,  with 
flowers  of  many  and  brilliant  hues,  resembling  the  flora  of 
the  Alps.  The  term  Flora  meaus  the  total  plant  life  of  a 
region.  The  flora  of  Ehode  Island,  for  example,  is  the  en- 
tire assemblage  of  plants,  large  and  small,  living  within  the 
State. 

283.  Water-loving  plants. — All  plants  require  water,  but 
some  have  become  fitted  to  live  with  very  little,  while  oth- 
ers require  much.  In  the  latter  class  we  find  many  kinds. 
In  the  waters  off  the  seashore  are  many  humble,  flowerless 
plants  known  as  seaweeds.  If  we  row  our  boat  over  the 
shallow  waters  of  any  pond  or  lake,  we  look  down  upon 
plants  that  are  perfectly  submerged,  even  though  they 
stand  upright  and  are  of  considerable  height.  If  we  pull 
one  of  these  stems,  we  find  it  limp.  It  is  supported  by  the 
water,  and  does  not  need  a  strong,  woody  stalk,  like  an 
open-air  plant.     It  may  have  poor  roots  also,  since  it  takes 


Fig.  222.— a  mountain  view  in  Colorado,  showing  the  grouping  of  plants  with  refer- 
ence to  water.  In  the  lakelet  are  yellow  pond-lilies,  then  a  belt  of  swamp-grass, 
a  belt  of  shore  bushes,  and  finally  a  pine  forest  on  firm,  dry  laud. 


326    AN  INTRODUCTION  TO  PHYSICAL   GEOGRAPHY 

its  food  less  from  the  soil  than  from  the  water.  Other 
plants,  like  the  water-lily,  are  well  rooted,  and  the  stems 
submerged,  but  their  leaves  rest  on  the  water,  and  their 
blossoms  rise  a  little  above  it.  Multitudes  of  lowly  plants 
are  not  attached,  but  move  or  float  free  in  the  water. 

Swamp  plants  root  in  water  or  very  wet  earth  and  rise 
more  or  less  above  the  water  surface.     Reeds,  rushes,  and  cat- 


4 


f 


Mi^' 


'r/0_J^ 


'*yf*^. 


Fig.  '^2'6. — An  ana  plum  m  iiortiR-ni  Anzoiia,  .scaiuiiy  ciouica  wiiii  low  bushes.     On 
the  distant  hills  is  the  beginning  of  the  juniper  zone. 

tail  flags  are  good  examples  of  these,  and  may  be  seen  on  the 
l?orders  of  any  pond.     There  the  conditions  of  plant  life  ar^ 


LIFE 


327 


about  half-way  between  those  of  water  and  those  of  land. 
In  swamps  are  found  the  cup-like  leaves  of  the  pitcher- 
plant,  the  spongy  mat  of  the  sphagnum  moss,  and  the  fruit- 
ful cranberry.  Upland  trees  assume  special  characters  when 
growing  on  swampy  ground,  and  the  great  swamp-cypress 
of  the  Southern  States  is  never  found  on  drier  land. 

284.  Dry  plains  and  deserts. — As  we  pass  from  the  prai- 
ries, or  natural  meadows,  westward,  we  find  the  plants  be- 


PiG.  224.— A  tree-yucca  on  a  desert  of  southern  California. 

coming  more  scattered  and  of  fewer  kinds,  consisting  mainly 
of  bunch-grasses  and  low  bushes.  The  region  is  not  a  des- 
ert, but  affords  a  certain  amount  of  pasturage.  Wide  ranges, 
however,  are  needed  for  herds,  in  comparison  with  well- 
grassed  regions. 


328    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


Farther  south  and  west,  areas  of  true  desert  begin.  Parts 
of  western  Texas,  Xew  Mexico,  Arizona,  Nevada,  Utah, 
southern  California,  and  Mexico,  fall  in  this  class.  Ordi- 
nary plants  could  not  live  in  such  heat  and  drought.  Some 
desert  plants,  as  the  cactuses,  have  no  leaves  to  exhale  the 
moisture.  Others  have  only  a  few  small  leaves  and  shed 
them  in  early  summer.  Yet  others,  like  the  larrea,  Spanish 
bayonet  and  agave,  have  varnished  leaves,  from  which  there 
is  little  evaporation.  All  stand  wide  apart,  so  that  each 
plant  may  have  a  large  patch  of  soil  to  store  for  it  the 
scanty  rain,  and  some  send  their  roots  to  great  depths. 

Animals  of  Nokth  Amekica 

We  have  grouped  the  plants  mainly  according  to  the 
conditions  in  which  they  thrive.  It  is  not  so  easy  to  do  this 
in  the  case  of  animals,  for  while  plants  are  generally  at- 
tached to  the  soil,  animals  often  range  freely  over  long  dis- 
tances. But  animals,  too,  are  dependent  on  climate.  Some 
dwell  on  the  ground,  others  in  the  soil,  and  yet  others  move 
freely  in  the  air.  Many  can  live  only  in  the  water,  and 
some,  like  the  frog,  or  the  beaver,  are  at  home  in  the  water 

or  on  the  land,  dividing 
their  lives  between  the 
two. 

285.  Animals  of  the 
North.— On  the  tundras 
of  Alaska  and  northern 
Canada  are  polar  bears, 
arctic  wolves,  foxes  and 
hares,  lemmings,  and,  at 
the  east,  herds  of  musk- 
oxen.  Most  of  these 
have  whitish  fur,  so  that 


Pig.  225.— The  musk-oxen  inhabit  tundms  and 
barren  grounds  of  the  far  North.    See  Fig.  226. 


they  are  not  easily  seen 
against  a  background  of  snow.  The  barren-ground  cari- 
bou, closely  resembling  the   Lapland  reindeer,  roams  the 


Fig.  226.— Distribution  of  the  inusk-ox,  moose,  and  antelope.  The  country  of  the 
musk-ox  is  shown  by  orange  ;  that  of  the  moose  by  green  ;  that  of  the  antelope, 
in  the  year  1900,  by  purple. 


LIFE 


329 


country  in  vast  herds.  In  neighboring  forests,  brown  and 
black  bears  abound,  with  the  moose,  woodland  caribou, 
and  lynx.  The  fisher,  otter,  marten,  and  mink  are  still  nu- 
merous, though  re- 
duced by  long  hunt- 
ing for  their  furs. 
The  beaver  is  still 
common  in  Canada 
and  in  some  parts  of 
the  United  States. 
"  This  very  intelli- 
gent animal  is  the 
chosen  emblem  of 
Canada,  for  it  is  at 
home  in  the  woods 
and  water."  (Daw- 
son.) 

At  least  600  kinds  of  birds  live  in  Canada,  most  of  which 
spend  the  summers  and  breed  there,  but  escape  the  ice  and 
snow  of  winter  by  flying  southward.    As  we  might  expect 

from  the  wide  for- 
ests and  thousands 
of    lakes,     ducks. 


Pig.  227.— The  woodland  caribou  inhabits  the  forests 
of  Canada  and  Alaska.  See  Fig.  231.  (Copy- 
righted by  Forest  and  Stream.) 


geese, 


and    other 


water  -  fowl  are 
found  in  countless 
numbers. 

286.  Animals  of 
the  temperate  re- 
gions. —  These  re- 
gions include  much 
of  southern  Cana- 
da and  nearly  the 
whole  of  the  Unit- 
ed States.  They  include  also  great  differences  of  animal 
life,  if  the  mountains  and  the  plains,  the  North  and  the 


Fig.  228.— The  moose  lives  in  northern  forests.    See 
Fig.  226.    (Copyrighted  by  Forest  and  Stream.) 


330    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


Fi0.  229.— The  antelope,  or  pronghorn,  oc- 
cupies open  country  on  the  Great  Plains 
and  westward.  See  Fig.  226.  (Copy- 
righted by  Forest  and  Stream.) 


■HHJII'  South,  are  compared.      In 

^^^»^  the  forests  of  the  West  live 

|K       J    I  elks,     and     bears,     black, 

brown,  and  grizzly ;  about 
crags  and  peaks  climb 
mountain  sheep  and  moun- 
tain goats ;  and  antelopes 
roam  the  open  lowland. 
All  these  large  animals  are 
numerous,  though  less 
abundant  than  formerly. 
Buffaloes  once  ranged  the 
Great  Plains  of  the  United 
States  and  Canada  in  mil- 
lions, so  that  the  land  was 
sometimes  black  with  them. 
It  is  believed  that  not  more 
than  50  now  survive  in  a 

wild  state.    With  ruthless  hand  man  has  destroyed  them, 

for  sport  or  for  the  sale  of  their  hides,  and  so  we  have  a 

striking  example  of  how  man  is  changing  the  animal  popu- 
lation of  the  world. 

The      destructive 

jack  -  rabbits     and 

prairie-dogs  of  the 

plains      are      less 

worthy  to  survive, 

but  better  able  to 

hold    out    against 

the  attack  of  man. 

Bears  and  wildcats 

are  found  in  all  the 

forests  of  the  East, 

and  deer,  under  the 

protection    of    the 

game     laws,      are 


Fig.  230.— The  white-tail  or  Virginia  deer  lives  in  tem- 
perate forests  from  the  Atlantic  coast  to  the  Rocky 
Mountains.  Its  range  grows  smaller  as  the  lands 
are  cleared.  See  Fig.  231.  (Copyrighted  by  Forest 
ftnd  Streftm,) 


Fig.  231.— Distribution  of  the  caribous,  white-tail  deer,  and  peccaries.  The  sum- 
mer range  of  the  barren-j^round  caribou  is  shown  by  bUie  ;  the  range  of  the  wood- 
land caribou  by  bars  of  darker  blue  ;  the  country  of  the  deer  by  yellow ;  the 
country  of  the  peccaries  by  red. 


LIFE 


331 


abundant.  In  the  Adirondack  woods  and  the  woods  of 
Maine  more  than  10,000  deer  are  annually  killed. 

287.  The  southern  lands. — Here  the  animals,  like  the 
plants,  change  to  tropical  kinds.  The  tapir,  jaguar,  and 
many  monkeys  inhabit  Central  America  and  parts  of  Mex- 
ico. Armadillos  and  peccaries  flourish  as  far  northward  as 
Texas,  and  opossums  northeastward  to  New  York.  Bril- 
liantly plumed  birds 
and  venomous  serpents 
tell  of  more  southern 
latitudes.  Serpents  of 
all  kinds  diminish  to- 
ward the  north,  and  are 
unknown  in  Alaska 
and  northern  Canada. 

We  must  not  omit 
the  most  abundant  of 
all  animals,  the  count- 
less insect  hosts  that 
swarm  from  farthest 
north  to  farthest  south. 
So,  too,  all  fresh  waters 
are  full  of  life.  Lakes 
and  rivers  teem  with 
fish,  and  even  the  soil 

is  honeycombed  with  Fig.  ^232.  The  home  of  the  peccaries  is  in 
,■,  ,^  J,  ,1  the  thickets  and  forests  of  tropical  lands. 

the    paths     of     earth-  g^^  ^jg  ^^ 

worms    or     burrowing 

moles,  gophers,  woodchucks,  and  prairie-dogs.  The  conti- 
nent is  filled  with  animals  and  plants  on  its  lands,  in  its 
soil,  in  its  waters,  and  in  the  atmospheric  sea  that  rests 
upon  it.  Each  condition  of  temperature  and  each  sort  of 
abode  has  its  own  groups  of  living  things. 

We  shall  now  study  the  principles  that  are  illustrated 
by  the  plants  and  animals  of  our  own  or  of  any  other 
continent. 


332    AN  INTRODUCTION  TO   PHYSICAL  GEOGRAPHY 


Geogkaphic  Conditions  of  Life 

288.  Temperature. — Neither  plants  nor  animals  can  ordi- 
narily live  and  be  active  in  temperatures  below  30°  or  above 
120°  F.  They  may  for  a  time  endure  greater  extremes, 
as  when  plants  survive  the  low  temperatures  of  winter  or  a 
man  toils  in  a  drying-room  of  some  factory.  Certain  arctic 
animals  are  protected  against  great  cold  by  coverings  of  fat 
and  fur,  and  certain  lowly  plants  live  at  higher  tempera- 
tures in  the  waters  of  hot  springs,  but  the  range  of  90° 
above  given  is  all  that  life  can  usually  endure  for  a  long 
time.  As  we  have  seen  in  studying  the  life  of  our  own 
continent,  the  range  is  not  the  same  for  all  forms ;  ser- 
pents and  monkeys  can  not  live  in  the  arctic  zone,  nor 
polar  bears  and  reindeer  in  the  far  South.  Cotton  belongs 
in  the  Gulf  region,  corn  in  the  prairie  and  Middle  Atlantic 
States,  and  wheat,  overlapping  the  corn,  will  thrive  far 
north  in  Canada,  in  regions  too  cold  for  the  taller  cereal. 
The  life  depends  on  the  latitude,  because  the  latitude  de- 
termines the  amount  of  heat.  At  the  foot  of  the  Eocky 
Mountains  in  Colorado  is  a  mild  climate,  with  bushes  and 
cactus  on  the  plains,  with  cottonwood  along  the  streams, 
and  with  grain,  alfalfa,  and  abundant  fruits  wherever  the 
land  is  cultivated  with  aid  of  irrigation.  Up  the  moun- 
tainsides are  evergreen  trees.  Beyond  the  trees  are  alpine 
flowers,  and  above  the  flowers, « rock,  snow,  and  chilling 
winds.  The  same  story  is  told  if  we  ascend  Mount  Etna, 
the  Alps,  or  any  other  lofty  mountains  rising  out  of  a  warm 
country.  All  grades  of  temperature,  to  those  of  arctic 
climes,  characterize  the  different  parts  of  a  great  mountain. 
Thus  altitude  vies  with  latitude  in  deciding  how  much 
heat  a  place  shall  have,  and  what  plants  and  animals  shall 
live  and  thrive.  By  shedding  their  leaves,  or  by  the  annual 
death  of  the  open-air  stem,  plants  may  endure  great  cold 
in  winter.  By  natural  or  artificial  covering,  animals,  in- 
cluding man,  provide  for  extremes   of  temperature;  but 


Fig.  233.— a  palmetto  grove.  Most  of  the  palms  are  tropical  plants  ;  but  the  pal- 
metto follows  the  Atlantic  coast  northward  to  North  Carolina.  It  is  the  cixoseu 
emblem  of  South  Carolina. 


334    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


heat  and  cold  decide  largely  what  creatures  shall  fill  a 
region. 

289.  Water. — No  life  can  be  carried  on  without  water. 
The  greater  part  of  all  animal  bodies,  and  of  many  plants, 
is  water.  It  supplies  food,  or  it  serves  as  a  moving  fluid  to 
carry  food  to  all  parts  of  the  body — as  the  blood  of  higher 

animals  and  the  sap  of 
trees.  We  have  seen 
that  plants  in  particu- 
lar show  the  greatest 
differences  in  respect 
to  water.  Some  live 
in  the  desert,  others 
in  places  of  alternate 
moisture  and  drought, 
others  root  in  moist 
soil,  and  yet  others  are 
partly  or  wholly  cov- 
ered by  water.  The 
cactus  sends  out  spines 
instead  of  leaves,  and 
grows  a  stocky  trunk, 
to  avoid  breathing  all 
its  water  into  the  dry 
air.  The  tree  braces 
itself  with  many  roots, 
rises  high  and  strong  into  the  air,  and  requires  a  moderate 
supply  of  water.  The  water-lily  has  a  limber  stalk  and  a 
limber  leaf,  because  the  water  bears  both  up,  and  the  water 
and  wet  soil  below  it  nourish  the  plant.  With  the  most 
heat  and  the  most  water  we  find  the  most  luxuriant  plant 
growth  of  the  world— the  tropical  forest.  With  the  most 
heat  and  the  least  water  we  find  the  opposite  condition — 
the  desert. 

290.  The  atmosphere. — This  is  essential  to  all  life.  In  a 
general  sense  all  creatures  "  breathe  "  the  air.     The  higher 


Fig.  234. —  Dam  and  pond  made  by  beavers; 
Wyoming.  The  beaver  makes  his  home  in 
streams  and  uses  great  skill  in  controlling 
the  water  to  suit  his  needs. 


336    AN  INTRODUCTION  TO  PHYSICAL   GEOGRAPHY 

animals  have  yarious  devices,  such  as  lungs  and  gills,  by 
which  they  take  in  large  amounts.  Man  and  the  other 
warm-blooded  animals  use  by  far  the  most,  but  all  lowly 
animals  and  all  plants  must  have  air,  and  have  some  means 
of  absorbing  it.  This  is  true  even  of  those  that  are  covered 
by  water,  and  at  great  depths.  At  the  bottom  of  the  sea, 
for  example,  air  is  present,  though  in  minute  quantities. 
The  roots  of  the  swamp-cypress  illustrate  a  special  device. 
They  are  in  submerged  soil,  and  send  up  short,  blunt  ex- 
tensions known  as  "knees,"  above  the  water  surface.  If 
the  water  is  raised  to  cover  the  knees,  the  tree  dies,  for  it 
is  the  work  of  these  parts  to  receive  air,  which  otherwise 
can  not  reach  the  roots. 

291.  Light. — This  is  required  by  nearly  all  life  and  by 
all  high  forms.  The  higher  plants  can  not  live  without  it ; 
submerged  plants  survive  with  a  partial  supply.  The  de- 
pendence of  plants  on  light  is  illustrated  by  the  pale  and 
feeble  growth  of  vegetables  in  a  cellar,  even  though  mois- 
ture and  heat  be  fully  supplied.  Thus  we  may  explain  the 
appearance  of  close  forests,  in  which  each  tall,  bare  trunk 
bears  a  canopy  of  limbs  and  leaves  like  an  umbrella.  As 
the  tree  grows,  the  lower  branches,  condemned  to  the  shade, 
die  and  fall  off,  while  the  top  branches  thrive  in  the  sun- 
light. The  arrangement  of  branches  on  a  trunk  and  of 
leaves  on  a  branch  is  such  as  to  expose  the  most  leaf  surface 
to  the  sun.  Exceptions  to  the  general  rule  are  found  in 
burrowing  creatures,  like  moles  and  earthworms ;  in  cavern 
fishes  and  cavern  insects,  surviving  for  generations  in  the 
darkness,  and  partly  or  wholly  losing  their  eyes  for  lack  of 
use ;  and  in  creatures  in  the  depths  of  the  sea,  where  sun- 
light does  not  penetrate,  and  darkness  is  only  relieved  by 
such  phosphorescent  glow  as  their  own  bodies  can  furnish. 

292.  Soils. — The  plant  groups  on  land  depend  directly 
on  the  soil,  in  connection,  of  course,  with  the  supply  of 
heat  and  water.  Some  soils  contain  calcium  carbonate, 
others  are  of  clay,  and  some  are  almost  wholly  made  up  of 


LIFE  337 

sand.  Sand  supports  but  a  partial  covering  of  plants,  as 
the  scant  grasses  and  scrubby  pines  of  dunes.  The  nature 
of  the  soil  also  controls  the  water  supply.  Sand  parts  with 
water  too  easily,  while  a  clay  soil  holds  it  so  tenaciously 
that  artificial  drainage  by  ditches  and  tile  is  often  needed. 

293.  Climate.— This,  as  we  have  seen,  is  determined  by 
many  conditions  of  heat,  moisture,  and  seasonal  change, 
and  plants  and  animals  in  any  region  must  adapt  them- 
selves to  these  conditions,  or  migrate,  or  perish.  Some 
plants,  as  certain  mosses  or  lichens,  may  dry  up  entirely 
in  a  period  of  drought,  and  revive  when  moisture  comes 
again.  Many  survive  the  winter  by  maturing  in  the  au- 
tumn seeds  which  lie  in  the  ground  and  sprout  in  the  spring. 
Others,  as  many  bulbous  plants,  die  down  to  the  surface  of 
the  ground,  and  the  underground  stem  lives,  to  start  the 
growth  of  the  next  season.  Broad-leaved  trees  drop  their 
leaves  in  winter,  and  quickly  put  them  on  again  with  the 
renewal  of  warmth.  Evergreen  trees  have  small,  tough, 
enduring  leaves,  which  are  proof  against  the  frosts  of 
winter.  Some  animals  lie  dormant  through  the  winter, 
neither  eating  food  nor  wasting  the  tissues  of  their  bodies 
by  activity.  Birds,  whose  swift  flight  gives  them  inde- 
pendence, adapt  themselves  to  the  changes  of  season  by 
migration  to  remote  regions,  all  save  those  which  have  ac- 
customed themselves  to  the  pinch  of  winter  and  to  living 
upon  buds,  and  other  supplies  that  do  not  fail. 

294.  Other  animals  and  plants.— Heat,  light,  and  air  are 
hardly  more  important  to  a  living  form  than  the  animals 
and  plants  by  which  it  is  surrounded.  Animals  find  in 
other  animals  their  friends  and  foes,  and  of  plants  we  may 
truly  say  the  same.  Not  less  is  it  true  that  animals  and 
plants  influence  each  other,  helping  or  destroying.  Some 
illustrations  of  these  relations  will  be  given  as  we  proceed. 

295.  Environment. — All  surrounding  nature  is  important 
to.  the  plant.  The  earth,  the  sun  and  sky,  and  all  living 
things  about  it,  make  up  what  we  call  the  Environment, 


338    AN  INTRODUCTION  TO   PHYSICAL  GEOGRAPHY 

which  is  only  a  scientific  word  for  the  total  surroundings 
of  an  animal  or  plant.  We  have  just  been  studying  the 
elements  or  parts  of  environment — namely,  temperature, 
water,  atmosphere,  light,  soil,  and  other  living  things.  The 
environment  largely  but  not  wholly  decides  what  a  plant 
or  animal  shall  be. 

296.  The  tendency  to  spread. — Single  plants  usually  ripen 
many  seeds,  and  some  plants  mature  them  by  hundreds  or 


Fig.  236.— The  spreading  of  the  English  sparrow.  The  large  dots  show  places  where 
the  sparrow  was  introduced  by  man  from  1852  to  1870,  and  the  small  dots  the 
country  over  which  it  had  spread  by  1886.  The  circles  show  additional  introduc- 
tions to  1886,  and  the  broken  lines  the  extent  of  spreading  from  1886  to  1898. 


thousands.  We  may  say  in  a  figurative  way  that  every 
plant  tries  to  occupy  as  much  ground  as  possible,  taking 
possession  wherever  there  is  an  opening  and  pushing  out 
into  wider  fields,  so  far  as  soil,  moisture,  and  other  condi- 
tions are  favorable.  The  same  is  true  of  animals.  Thus 
the  buffaloes  multiplied  until  they  virtually  possessed  the 
Great  Plains.  If  a  single  pair  of  birds  should  be  placed  in 
a  favorable  region  and  no  accident  should  happen  to  them 
or  to  their  offspring,  their  descendants  would  in  a  few 
years  be  numbered  by  thousands  and  spread  over  a  wide 


LIFE  339 

field.  A  heavy  fine  is  said  to  be  the  penalty  for  bringing  a 
white  daisy  into  Minnesota.  It  might  diffuse  itself  over 
the  entire  State,  bringing  untold  harm  to  the  farmer.  A 
few  years  ago  a  foreign  insect  known  as  the  gipsy-moth 
was  brought  into  eastern  Massachusetts.  In  the  caterpil- 
lar stage  it  preys  upon  the  foliage,  and  it  has  filled  New 
England  with  alarm  lest  the  trees  be  destroyed.  Large 
sums  have  been  expended  by  the  State  of  Massachusetts  to 
check  its  spread. 

297.  The  struggle  for  existence.— Thus  we  see  how,  if 
left  to  itself,  any  animal  or  plant  would  take  possession  of 
all  the  land  or  water  where  it  could  live,  if  it  met  no  impass- 
able barrier.  But  the  space  is  limited,  and  so  each  group 
of  plants  as  well  as  each  individual  has  to  contend  with 
every  other.  The  oaks  can  not  fill  the  forest  because  the 
chestnut,  ash,  and  maple  are  there.  In  a  thicket  of  young 
maples,  not  all  can  grow  up  to  be  large  trees.  Those  will 
win  which  have  the  best  roots,  the  deepest  soil,  the  best  ex- 
posure to  the  sun,  or  suffer  no  injury  from  beast  or  man. 
Thus  we  explain  what  is  meant  by  the  now  common  phrase. 
Struggle  for  Existence.  It  is  not  usually  a  conscious  strife, 
but  it  is  the  silent  contest  going  on  among  competing 
plants  and  animals.  Fishes  produce  vast  numbers  of  eggs, 
part  of  which  are  devoured  or  otherwise  perish,  while  the 
remainder  hatch.  But  of  the  multitudinous  ''  fry  "  only  a 
small  part  arrive  at  maturity.  Many  die  of  accident,  or 
from  failure  to  get  food,  or  fall  a  prey  to  other  fishes,  and 
out  of  such  a  "  struggle  "  only  the  strong  or  the  fortunate 
reach  full  size  and  live  to  their  natural  limit.  In  some 
regions  the  white  oaks  are  said  to  be  falling  behind  in  the 
struggle  with  other  oaks,  because  their  acorns  are  more 
prized  by  squirrels  and  diligently  sought  by  them.  Thus 
by  an  innocent  preference  of  the  squirrel,  one  kind  suffers 
and  the  others  win  in  the  struggle.  Let  us  take  again  the 
case  of  the  tree.  A  beech  may  produce  thousands  of  nuts 
in  a  single  season.     These  seeds  are  eagerly  gathered  by 


340    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

forest  animals.  If  they  escape  this  fate,  they  may  ger- 
minate and  drive  a  root  into  the  soil.  But  even  then,  in 
the  thick  of  the  forest  the  chances  are  vastly  against  the 
sapling.  Taking  the  seeds  of  plants  and  the  eggs  and  infant 
offspring  of  animals,  especially  of  lowly  sorts,  only  one  in 
many  thousands  is  likely  to  produce  a  mature  life. 

298.  Migration. — Animals  and  plants  often  succeed  in 
the  struggle  for  existence  by  migrating.  All  plants  scatter 
their  seeds  somewhat,  and  some  strew  them  broadly.  The 
dandelion  provides  them  with  plumes  that  the  wind  may 
carry  them,  the  burdock  hooks  them  to  the  hair  of  animals, 
and  there  are  many  other  devices.  So  each  plant  tends  to 
increase  its  range  and  spread  as  widely  as  it  can  find  suit- 
able environment.  When  the  cold  of  the  Glacial  period 
came  on,  each  kind  of  plant  found  life  harder  at  the  ^N^orth 
and  easier  at  the  South,  and  so,  in  the  course  of  generations, 
its  range  was  reduced  on  one  side  and  extended  on  the 
other.  Individuals  were  killed,  but  the  race  gradually  mi- 
grated toward  the  south.  The  plant  species  which  could 
easily  send  seeds  southward  survived,  and  any  which  could 
not  migrate  perished.  This  is  the  sense  in  which  fixed 
plants  can  migrate — that  is,  from  generation  to  genera- 
tion. Land  animals  and  free-swimming  oceanic  animals 
can  migrate  as  individuals,  and  the  birds,  as  we  have 
seen,  for  the  greater  part,  are  in  the  habit  of  periodic 
migration. 

299.  Helps  and  hindrances  to  migration.— Some  of  the 
devices  that  favor  the  spread  or  migration  of  plants  have 
been  noticed.  Such  are  the  hooks  of  the  burdock  and  the 
plumes  of  the  dandelion.  Other  seeds  have  a  hard  covering 
which  protects  them  against  destruction  in  the  crops  of 
birds,  and  they  may  thus  be  dropped  after  being  carried 
long  distances.  Seeds  embedded  in  soil  or  mud  are  carried 
on  the  hoofs  of  beasts  or  the  claws  of  birds.  Since  man  has 
come  upon  the  earth,  multitudes  of  seeds — some  good,  some 
bad — have  been  diffused  over  the  earth  by  him.    Such 


LIFE  341 

is  the  so-called  Eussian  thistle,  whose  roundish  tuft  of 
branches  breaks  oif  at  the  ground  and  is  rolled  and  driven 
widely  by  the  winds  over  the  Great  Plains.  The  restric- 
tions upon  the  importation  of  fruit,  meat,  and  other  articles, 
by  various  nations,  illustrate  the  human  agency  in  distrib- 
uting the  germs  of  life. 

Floating  timber  and  roots  may  transport  seeds,  plants, 
and  even  small  animals,  for  long  distances  down  rivers,  and 
even  across  seas.  It  has  been  shown  that  some  seeds  may 
live  after  long  journeys  in  sea- water.  This  helps  to  explain 
how  new  islands  in  the  ocean  obtain  a  covering  of  plants. 
As  we  have  seen,  swimming  and  flying  animals  have  an  ad- 
jVantage.  The  beasts  of  continents  can  not  reach  remote 
islands  unless  carried  there  by  man.  But  the  birds  are 
there,  because  they  have  the  means  of  traveling  over  the 
waters,  being  often  blown  out  by  storms,  and  alighting 
there  for  refuge. 

We  have  now  begun  to  see  that  migration  is  hindered  or 
prevented  by  Barriers.  The  sea  is  an  absolute  barrier  to 
most  land  plants  and  animals.  The  wider  the  sea  the  com- 
pleter the  barrier.  Hence  lands  with  the  same  climates 
may  have  very  different  groups  of  animals.  Thus  in  Aus- 
tralia, South  Africa,  and  South  America  are  found  very 
similar  conditions,  but  the  animals  and  plants  are  different 
because  there  has  been  no  chance  for  them  to  mingle,  and 
each  continent  has  developed  its  own  kinds  of  life.  Islands 
have  a  life  of  their  own,  except  as  migration  is  possible,  or 
has  been  at  some  time  possible,  or  the  hand  of  man  has 
interfered.  So  far  as  islands  resemble  continents  in  their 
animals  and  plants,  they  are  like  the  nearest  continents. 
The  Galapagos  Islands,  for  example,  resemble  South  Amer- 
ica, and  the  Cape  Verde  Islands,  western  Africa,  in  their 
life.  Hawaii  is  far  from  large  lands  and  has  no  large  mam- 
mals or  snakes. 

Lands  serve  as  barriers  between  seas,  and  hence  the 
ocean  forms  differ  on  opposite  sides  of  the  Isthmus  of  Paxi- 


342     AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

ama.  There  is  some  likeness,  however,  and  this  shows  that 
the  waters  have  some  time  crossed  where  the  isthmus  now 
lies.  So  too  the  life  of  the  Red  Sea  is  not  like  that  of  the 
Mediterranean.  The  English  Channel  is  a  narrow  water 
barrier  between  England  and  the  Continent.  It  has  not 
always  been  there,  and  in  the  days  of  land  connection  wild 
animals  went  freely  to  and  fro,  which  explains  the  close 
resemblance  of  the  native  animals  of  Great  Britain  to  those 
of  the  rest  of  Europe. 

300.  Dependence  of  animals  and  plants.— The  animal  and 
plant  kingdoms  belong  to  each  other  in  many  ways.  First, 
we  have  the  familiar  fact  that  most  of  the  higher  land  ani- 
mals depend  on  plants  for  food.  And  beasts  of  prey,  in 
devouring  other  animals,  depend  indirectly  on  plants  for 
life.  Vegetation  is  the  only  means  by  which  the  minerals 
of  the  soil  can  be  changed  into  food  for  land  animals — in- 
sect, beast,  or  man. 

We  have  seen  that  by  direct  carriage  of  seeds  or  roots, 
animals  foster  the  wider  distribution  of  plants.  But  the 
botanist  and  zoologist  know  of  many  more  intimate  and 
curious  ties  that  bind  plants  and  animals  together.  In- 
sects are  protected  by  taking  on  certain  colors,  as  the  green 
of  forest  or  meadow.  Worms  may  mimic  the  color  and 
even  the  forms  of  branching  twigs,  and  thus  escape  ene- 
mies. The  tiger  is  not  easy  to  see  in  the  jungle  because 
its  stripes  confuse  it  with  the  upright  lines  of  light  and 
shadow  of  luxuriant  plants. 

We  find  also  that  insects  and  flowering  plants  have 
much  to  do  with  each  other.  Many  plants  would  never  be 
fruitful  if  insects  did  not  drop  the  pollen  of  one  flower 
upon  the  pistils  of  another.  And  insects  and  plants  have 
become  adapted  to  each  other  by  this  means.  Some  in- 
sects seek  the  pollen  itself,  and  others  seek  the  nectar  of 
the  flower  for  food,  but  in  any  case  the  result  is  the  trans- 
fer of  the  pollen.  Darwin  describes  a  red  clover  which 
Qould  not  live  without  the  visits  of  bumblebees ;  the  honey- 


LIFE 


343 


bees  can  not  reach  deep  enough  into  the  flower  tubes  to  get 
the  nectar.  Hence  any  enemy  that  should  destroy  the 
bumblebees  would  make  it  impossible  to  raise  this  kind  of 
clover. 

801.  Life  of  the  ocean. — Some  facts  have  been  learned  in 
previous  chapters.  The  ocean  has  its  regions  and  groups 
of  forms  as  well  as  the  land.    Deep  water  is  a  perfect  barrier 


Fig.  237.— Sea-lions,  Santa  Catalina  Islands,  California.  Though  these  animals  are 
thoroughly  fitted  for  the  sea.  and  subsist  on  cuttle-fishes,  it  is  thought  that  their 
remote  ancestors  lived  on  the  land  and  resembled  bears. 


to  shallow-water  forms,  and  if  they  should  migrate  along  the 
shores  they  might  find  warmer  or  colder  water  that  would 
be  fatal  to  them.  Corals  belong  in  warm  seas,  walruses 
thrive  in  northern  waters,  and  each  is  as  characteristic  of 
its  zone  as  palms  and  polar  bears  are  of  the  land  zones. 
The  whale  is  a  great  specialized  mammal,  whose  ancestors 
^re  believed  to  have  lived  on  the  land.    It  has  developed  its 


344    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


fore  limbs  into  paddles  and  its  tail  into  a  powerful  rudder, 
but  has  only  partly  become  fitted  for  life  in  the  water,  for 
it  must  come  to  the  surface  to  breathe.  It  has  a  wide 
range  in  the  sea,  but  its  numbers  have  been  reduced  by 
man.  A  whale  was,  in  the  autumn  of  1901,  reported  as 
having  strayed  up  the  St.  Lawrence  as  far  as  Montreal. 

Oysters,  clams,  scallops,  and  other  so-called  shell-fish 
inhabit  the  shallow  waters  near  the  shore.  These  shelled 
creatures  (mollusks)  exist  in  enormous  numbers  and  have 


5 

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0tt/t^^^  ^^ 

^^^^ppj^f^^H 

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-^^^'''^m^ 

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^^C,  "r'-'^A 

1 

'M0^ 

p 

Fig.  238.— Crabs  living  in  shallow  water  of  the  ocean  ;  the  kelp  crab,  in  upper  part 
of  figure  ;  to  the  left  the  edible  crab  ;  and  to  the  right  the  shore  crab. 

shells  of  great  variety  of  form,  especially  in  tropical  waters, 
where  ornamentation  of  form  and  color  has  its  highest  de- 
velopment. With  them  are  starfishes,  thorny  sea-urchins, 
and  the  more  active  lobsters  and  crabs.  The  product  of  the 
seas  most  important  to  man  is  the  fish.  The  shoal-water 
fishes  and  the  deep-sea  fishes  furnish  the  study  of  a  life- 
time to  any  one  who  would  know  them  well. 

Let  any  one  go  into  what  we  call  the  silence  of  forest 
or  open  field  and  watch  and  listen.  It  is  a  world  of  sights 
and  sounds,  of  living  things.     Or  let  him  wander  by  the 


LIFE  345 

seashore,  and  look  into  the  pools  that  the  ehbing  tide 
leaves,  or  see  what  the  waves  cast  up.  The  sea  is  full  of 
life  also. 

If  we  would  know  something  of  the  living  world,  and 
would  understand  what  it  means,  we  must  also  learn  that  all 
creatures  have  come  down  from  a  remote  past,  and  that  the 
ancestors  of  herb  and  tree,  of  mollusk,  serpent,  bird,  and 
horse,  are  buried  in  the  rocks.  This  opens  the  realm  of 
geology,  which  ever  forms  the  background  of  geography. 


CHAPTER   XVI 

THE  EARTH  AND  MAN 

Man  is  more  widely  scattered  over  the  lands  than  any- 
other  animal.  He  is  not  confined  to  single  continents  or 
to  separate  zones,  although  some  races  or  tribes  have  become 
specially  adapted  to  hot  climates  and  others  to  cold  regions. 
The  man  of  temperate  latitudes,  by  his  greater  intelligence, 
is  able  to  live  and  work  for  years  in  the  arctic  or  in  the 
tropical  regions.  Man  may  not  live  among  the  rocks  and 
snows  of  the  highest  mountains,  in  the  driest  and  hottest 
deserts,  or  on  ground  covered  by  a  great  glacier,  as  central 
Greenland.  He  may,  however,  visit  all  these  places.  The 
only  regions  where,  so  far  as  we  know,  man  has  never  lived 
or  journeyed,  are  those  nearest  the  poles.  He  has  so  accus- 
tomed himself  to  safe  and  prolonged  travel  upon  the  ocean 
that  he  may  almost  be  said  to  occupy  the  great  waters  as 
his  home.  Like  the  plants  and  the  other  animals,  he  de- 
pends on  a  variety  of  conditions  which  make  up  his  envi- 
ronment. 

302.  Food.— Here  we  have  the  most  important  relation 
which  our  kind  holds  to  the  earth.  There  was  a  rude, 
primitive  man,  living  in  ages  now  long  past,  who,  in  simple 
ways,  got  his  food  from  the  life  that  was  about  him.  There 
were  herbs,  shrubs,  and  trees,  producing  nuts  and  other 
seeds,  wild  berries  and  other  fruits,  and  aifording,  beneath 
the  surface  of  the  soil,  juicy  stems  and  roots  which  could 
be  dug  by  fingers  or  sticks ;  and  various  small  animals  could 
be  caught  for  flesh.  At  length  rude  implements  of  chase 
were  invented,  such  as  flint  arrows  and  fish-hooks  of  bone, 
346 


THE  EARTH  AND  MAN 


347 


and  the  flesh  of  larger  animals  was  added  to  the  food  sup- 
ply. Flint  knives,  chipped  and  rough,  served  to  skin  the 
animals,  and  as  the  arts  of  fire  were  learned  cooked  food 
began  to  be  used. 

In  a  gradual  way,  through  the  ages,  foods  multiplied, 
until  now  the  world  is  ransacked  to  provide  for  the  table 
of  a  civilized  household.  Wild  plants  were  cultivated  and 
were  improved,  until,  in  many  cases,  all  traces  of  their  origi- 
nal condition  were  lost.     By  constantly  selecting  the  best, 


A  wheat-field  in  Washington.    Reaping  and  loading  by  machinery. 


and  by  tilling  and  enriching  the  soil  and  removing  other 
plants,  the  various  grains,  fruits,  and  vegetables  familiar  to 
us  have  been  developed.  Eocks  weather  into  soil,  water 
moistens  it,  the  sun  heats  it,  a  seed  is  provided,  a  plant 
spreads  its  leaves  in  the  air,  and  by  its  roots,  stems,  or 
fruit  man  lives.  The  great  foods  of  temperate  regions  are 
the  cereals  or  common  grains.  Wheat  is  one  of  the  most 
widespread.  Its  origin  is  unknown,  but  it  is  now  grown  on 
the  plains  of  Eussia,  the  prairies  and  plains  of  the  United 


348    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


States  and  Canada,  in  South  America,  Australia,  and  other 
parts  of  the  world.  Maize,  or  Indian  corn,  is  a  native  of 
America,  requires  a  warmer  climate  than  wheat,  does  not 
thrive  so  far  north,  and  is  one  of  the  most  important  grains 

of  America  and  of  other 
lands  as  well.  Barley, 
rye,  and  oats  agree  in 
their  adaptation  to  the 
cooler  temperate  cli- 
mates of  the  world,  as 
in  Canada,  northern  Eu- 
rope, and  Siberia,  and 
each  in  certain  regions 
is  the  most  important 
food  plant  raised  by  the 
people. 

Eice,  grown  in  many 
lands  where  heat  and 
moisture  abound,  is  the 
chief  food  in  vast  re- 
gions. In  China,  Japan, 
India,  and  the  East  In- 
dian islands  500,000,000 
people  live  mainly  upon 
it.  Other  plants  which 
thrive  in  warm  lands 
offer  an  abundant  food 
supply  obtained  with  lit- 
tle labor.  Here  belong 
the  fig,  the  various 
palms,  and  the  bread- 
fruit. The  temperate  regions  also  have  their  improved 
fruits,  such  as  the  apple,  pear,  peach,  and  many  berries,  all 
derived  from  wild  ancestors.  The  potato  is  the  most  im- 
portant example  of  a  tuber  or  underground  stem  used  for 
food.     It  is  a  native  of  South  America,  has  spread  to  other 


Fig.  340.— Maize. 


THE   EARTH  AND  MAN 


349 


continents  by  the  hand  of  man,  and  sometimes,  as  in  parts 
of  Ireland,  forms  the  principal  article  of  food.  A  great 
variety  of  plants 
could  be  named 
from  which  stimu- 
lating drinks  are 
brewed  or  distilled. 
Such  are  tea,  cof- 
fee, the  saps  of  va- 
rious plants,  many 
grains,  and  many 
fruits.  Here  also 
reference  may  be 
made  to  the  won- 
derful diffusion  of 
the  growth  and  use 
of  tobacco  in  mod- 
ern times. 

303.  Animal  food. 
— We  have  seen 
that  the  early  man 
sought  to  take  fish 
and  to  pursue  wild 
animals  as  his  prey. 
With  increasing 
skill  he  secured 
much  game,  as  did 
the  American  In- 
dian, with  his  use 
of  bow  and  arrow. 
In  course  of  time 
fishing  became  an 
art  pursued  by 
thousands  of  men 
on  lake,  river,  and  sea,  and  the  coastal  tribes  and  peoples 
have  always  thus  obtained  much   of  their  food.     Other 


Fig.  241.— a  tea-plantation  in  India. 
The  gathering  of  the  leaves. 


850    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


\ 


marine  animals,  like  the  oyster  and  lobster,  add  their  part 
to  man's  support.  But  most  important  of  all  have  been 
the  domesticated  animals,  from  the  time  when  Oriental 
tribes  had  their  chief  wealth  in  flocks  and  herds,  down 
to  the  present  day  of  great  stock-ranches,  stock-yards, 
and  refrigerator-cars.      Scarcely  second  to  the  flesh  food 

are  eggs  and  dairy- 
products  of  every 
kind.  It  is  con- 
venient here  to  ob- 
serve that  water  and 
common  salt  are 
the  only  mineral 
or  inorganic  sub- 
stances habitually 
taken  into  the  body 
by  man. 

304.  Clothing.— 
In  covering  and  pro- 
tecting his  body  man 
is  brought  into  an- 
other set  of  rela- 
tions to'  the  earth. 
The  earliest  men 
were  probably  un- 
clad, and  to  the 
present  time  little 
clothing  is  worn  by 
savages  living  in 
warm  climates.  The 
earliest  garments  were  rude  mantles  of  skin  taken  from 
animals,  or  fringes  or  plaitings  of  reeds  and  grasses.  Then 
came  primitive  weaving,  practised  somewhat  even  among 
wild  tribes  like  the  American  Indians.  Instead  of  wrap- 
ping skins  about  the  body  men  began,  like  the  Eskimos  of 
to-day,  to  cut  and  sew  them.    The  last  stages  in  the  growth 


^ 


Fig.  242.— Bow,  arrow,  and  deerskin  quiver  of  a 
Navajo  Indian. 


THE  EARTH  AND  MAN 


351 


of  dress  bring  us  to  the  highest  arts  of  the  loom  at  the  pres- 
ent time.    Here  the  animals  and  the  plants  contribute  almost 
equally  the  fibers  for  cloths  of  every  sort.     Chief  among 
plant  fibers  is  cotton— that  is,  the  silky  hairs  which  clothe 
the  cotton-seeds.     It  is  cultivated  in  the  warm  belt  extend- 
ing around  the  globe. 
It  was  known  in  ancient 
times,  but  does  not  go 
back    to    the     earliest 
days  in  Egypt  or  China. 
It    is   one    of   the   few 
commercial       products 
of  supreme  importance. 
Flax  furnishes  another 
vegetable     fiber,     well 
known    in    linen     and 
laces,   and    often    used 
for  sails  and  twine.     It 
thrives  in  a  wide  range 
of   temperature,    north 
and    south,    and     was 
used    in  remote  times. 
The    coarser    fibers   of 
hemp,  jute,  and  manila, 
which  we  know  chiefly 
in   cordage,   still   serve 
primitive    peoples     for 
clothing.      The  wool  of 
sheep  is  the  most  wide- 
ly  used   of   all    animal 
materials,  especially  in 
temperate  and  cold  latitudes,  and  the  fibers  of  the  silk- 
worm furnish  the  most  delicate  fabrics  that  the  art  of  man 
has  produced.     Gradually  perfection  has  been  reached  in 
the  tanning  of  skins,  particularly  for  foot  coverings ;  and 
furs  are  the  necessity  of  arctic  peoples  and  the  luxury  of 
24 


Fig.  243.— Cotton-picking  in  Georgia. 


352    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


dwellers  in  lower  latitudes.  The  feathers  of  birds  have 
long  furnished  favorite  ornaments,  and  man  also  draws 
directly  from  the  earth  the  lustrous  and  rare  minerals 
that  he  calls  gems  and  the  variety  of  objects  for  personal 
adornment  that  he  makes  from  the  precious  metals. 

305.  Tools  and  utensils. — Man  is  the  only  animal  that 
contrives  tools.  First  he  chipped  stones  into  arrow-heads, 
spear-heads,  and  knives.  Then  he  ground  and  smoothed 
them,  and  tied  stones  to  sticks  for  axes.  He  cut  bone  into 
scrapers,  awls,  and  needles,  and  beat  masses  of  native  cop- 
per into  useful  shapes.  His  great  progress  came  when 
he  learned  to  extract  metals  from  ores  and  could  fashion 
hard  and  sharp  instruments  of  iron.  Thence  the  unfold- 
ing never  stopped  until  the  in- 
tricate machinery  of  to-day  was 
contrived.  In  early  days  men 
wove  twigs,  roots,  and  leaves 
into  baskets  and  other  recepta- 
cles (Fig.  258).  They  found 
also  that  they  could  mold  clay 
into  useful  vessels  and  bake  it, 
so  that  it  would  resist  the 
influence  of  air  and  moisture 
(P^ig.  259),  and  this  has  led  on 
to  the  making  of  plastic  ob- 
jects as  delicate  and  beautiful 
as  jewels.  Another  mineral, 
the  quartz  of  every  bed  of 
sand,  provides  many  of  the 
most  ornamental  as  well  as  use- 
ful receptacles,  those  made  of 
glass. 

306.  Shelter. — Here  our  dependence  upon  the  earth  is 
as  close  as  it  is  in  the  supply  of  other  needs.  Caverns  were 
perhaps  the  first  shelters,  requiring  no  invention.  The 
forests  served  as  a  roof,  relieving  the  sun's  heat  and  the 


Fig.  244.— a  stone  ax  made  by  North 
American  Indians  ;  one-half  ac- 
tual size.  The  groove  is  for  tying 
on  the  handle. 


THE  EARTH  AND  MAN 


353 


force  of  winds,  but  offering  little  barrier  to  rains  and  chill- 
ing snows.  Huts  of  boughs,  thatched  with  leaves,  perhaps 
came  next,  and  in  colder  lands  dugouts  in  the  earth  or 
walls  of  turf  and  rough 
stones,  with  roofs  of  skin. 
Very  early  stones  were 
dressed,  and  the  temples 
of  Assyria,  Egypt,  Mexico, 
and  Peru  prove  that  skill 
to  quarry  and  build  is  of 
no  modern  growth.  Iron 
tools  made  it  possible  to 
use  the  wood  of  the  for- 
ests, to  hew,  saw  and  mor- 
tise it,  and  thus  to  provide 
cottages  for  the  poor  and 
palaces  for  the  rich.  The 
molding  of  bricks  and  the 
arts  of  carving,  plastering, 
and  painting  made  more 
complete  man's  mastery  of 
the  earth  for  shelter  and 
a  home. 

307.  Fuel  and  light— 
The  farther  north  or  south 
from  the  equator  man 
lived,  the  more  he  found 
fire  a  necessity,  if  he  was 
to  lead  better  than  an 
animal  life ;  so  the  supply  of  fuel  became  an  important 
problem.  For  a  long  time  the  forests  were  ample,  until 
increasing  population  and  foolish  destruction  of  trees 
had  partly  exhausted  this  supply.  Fat  and  animal  oils 
took  the  place  of  wood  in  cold  latitudes.  Then  coal  was 
found,  which  is  a  supply  of  woody  matter  and  of  mosses, 
leaves,  and  seeds  stored  away  in  ancient  forest  beds  and 


Fig.  245.— a  spear-head  of  flint ;  actual  size. 
Made  by  Osage  Indians,  Indian  Terri- 
tory. 


854  AN  iNTRODirCTION  TO  PHYSICAL  GEOGRAPHY 


gradually  changed  to  black  mineral.  In  a  few  regions 
natural  gas  can  be  obtained  for  heating  by  boring  down 
into  the  rocky  layers. 
Light,  too,  was 
needful  to  prolong 
the  day,  especially  in 
temperate  and  arctic 
regions,  where  the 
winter  nights  are  so 
long.  Fats  and  ani- 
mal oils,  as  of  the 
whale,  were  first  used, 
then  gas  distilled  from 
coal,  and  oil  from  the 


Fig.   24G.— Brush  shelters  used 
by  Indians  of  southern  Utah. 

refining  of  petroleum, 
and  now  has  come  the 
cleaner,  safer,  and  more 
brilliant  lighting  by 
electricity.  First  man 
lived  by  light  of  sun, 
moon,  and  stars  alone ; 
then  he  used  the  oil  of 
creatures  now  living, 
until  he  found  the  oil 
of  creatures  and  plants 
buried  for  ages  in  the 
rocks;   and  finally  he 

turns  to  one  of  the  great  forms  of  physical  force  for  his 

illumination. 


Fig.  247.— a  tepee,  or  Indian  skin  tent 
Wyoming. 


356    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


308.  Travel. — Let  us  now  see  how  man  has  used  the 
earth  in  moving  ahout  upon  it.  First  he  traveled  by  his 
legs  and  feet,  needing  no  invention.  Across  rivers  he  might 
swim,  but  over  lakes  and  arms  of  the  sea  he  must  be  floated 

if  he  went  at  all, 
and  for  this  the 
dugout  and  bark 
canoe  were  devised. 
With  the  domesti- 
cation of  horse  or 
ass,  he  mounted 
and  rode,  and  by 
and  by  a  rude  har- 
ness and  sledge  or 
simple  wheeled  ve- 
hicle advanced  him 
farther  in  the  arts 
of  travel.  Then 
progress  was  steady, 
from  the  paddle  to 
the  sail,  and  a'c 
length  to  the  pro- 
peller screw;  and 
on  land,  from  the 
sled  and  wagon  to  the  steam-car  and  the  electric  carriage. 
Navigation  of  the  air  must  be  counted  as  yet  in  its  begin- 
nings. 

With  the  invention  of  vehicles  has  gone  the  making  of 
roads  and  the  opening  of  routes  once  thought  impracticable. 
Fifty  years  ago  the  United  States  Government  carried 
several  lines  of  survey  across  our  western  mountain  ranges, 
to  see  where  railways  could  be  built  to  the  Pacific  coast. 
The  Colorado  route,  where  now  several  railways  cross,  was 
pronounced  impracticable.  Northern  Asia,  once  a  region 
of  a  few  wandering  tribes  and  of  convicts,  is  now  opened  to 
the  world  by  the  Siberian  Railway,  linking  St.  Petersburg 


Fig.  249. 


-A  log  cabin  and  rail  fence ;    Cumberland 
Plateau. 


Fig.  250.— a  carefully  graded  carrfage  road,  winding  up  from  the  Rhone  valley  to  an 
Alpine  pass.    The  view  shows  also  the  work  of  glaciers.    (See  pages  124  and  141.) 


-The  cog  railway  from  Manitou  to  Pikes  Peak,  Colo.    Even  for  climbing 
mountains  machinery  is  taking  the  place  of  muscles. 

307 


358    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


and  the  Pacific  Ocean.  Another  railway  is  projected,  from 
Cairo  to  Cape  Town,  to  make  a  highway  throughout  the 
length  of  the  African  continent.  Rivers  and  lakes  have 
made  a  great  network  of  inland  navigation.  Man  covers 
the  gaps  between  these  natural  waterways  by  making 
canals,  storing  water  at  the  summits,  and  letting  it  down  by 
locks  through  a  succession  of  levels.  All  valleys  invite  men 
to  easy  routes  of  travel.  The  trails  which  lead  among  hills 
and  mountains  are  followed  by  graded  roads  for  the  re- 
moval of  ores  or  timber,  and  often  by  rails  of  steel  over 
which  roll  trains  of  laden  cars.  In  his  travel,  as  in  provid- 
ing shelter,  raiment,  and  food,  man  is  closely  linked  to  the 
earth,  but  more  and  more  uses  it  with  triumphant  skill  and 
power. 

309.  Communication  and  record. — If  the  early  man  sent 
a  message,  he  told  it.  to  his  fellow,  who  carried  it  to  its 
destination.  Or,  if  he  desired  to  record  some  story  of  his 
experience,  he  made  a  rude  picture  by  bruising  or  scratch- 
ing the  face  of  a 
cliff.  Picture  lan- 
guage in  time  be- 
came elaborate  and 
was  written  on  rude 
paper  called  papy- 
rus, or  carved  on 
stone.  Such  records 
are  now  eagerly 
sought  by  students 
of  ancient  history 
in  Oriental  lands. 
Out  of  picture 
signs  grew  letters, 
and  picture-writing 
was  followed  by 
alphabetic  writing.  Manuscript  letters  and  manuscript 
books  were  succeeded  by  printed  books,  by  newspapers,  an^ 


')2. — A    (liiL'-out,  ;i    l)()at  carved   from  a  log  and 
propelled  by  a  paddle  ;  Alaska. 


THE  EARTH   AND  MAN 


369 


in  these  later  days 
by  the  electric  tele- 
graph and  the  tele- 
phone for  swift 
communication. 
As  wonderful,  if 
less  swift  in  its 
operations,  is  the 
modern  postal  sys- 
tem, covering  all 
civilized  lands  and 
bringing  messages 
of  friendship  and 
of  business  to  the 
door  of  many  mil- 
lions    of     people. 


Fig.  254.— La  Santa  Maria,  the  flagship  of  Columbus. 
Large  ships,  using  the  power  of  wind,  first  made 
great  voyages  possible. 


Fig.  253.— The  modern 
steamship  --  the  City 
of  New  York. 

Il^FLUEI^CE    OF 

Envieonme^s't 

We  have  seen 
how  man  satisfies 
his  wants  by  using 
the  minerals, 
plants,  and  ani- 
mals of  the  earth. 
It  is  also  easy  to 
see  that  he  meets 
these  wants  in  dif- 
ferent    ways,    ac- 


360   AN   INTRODUCTION  TO   PHYSICAL  GEOGRAPHY 


cording  to  the  kind  of  country  in  which  he  lives.     Warm 
and   cold   climates,  deserts   and   forests,  coast  lands   and 


Fig.  255.— Rock-carvings  by  Indians  of  Nebraska ;  a  pictorial  record  of  events. 

interior  lands,  all  influence  him  and  change  him.      This 
is  the  work   of    environment,   and   we   shall  now  select 


FiG.  256.— Picture-writins: ;  a  stage  In  the  development  of  letters.  The  Book  of  the 
Dead,  of  which  a  page  is  here  copied,  was  written  by  ancient  Egyptians  on 
papyrus. 

several  sorts  of  environment,  and  see  how  man  thrives  in 
each. 


THE  EARTH  AND  MAN 


361 


310.  Life  along  arctic  shore-lines. — Here  the  sea  is  of  first 
importance.  The  fishing  and  hunting  of  walruses  and  seals 
are  the  main  occupations,  and  almost  the  only  means  of 
maintaining  life.  Houses  are  built  of  earth  or  snow.  Skins 
are  the  only  clothing,  implements  are  fashioned  from  bones, 
fat  must  serve  for  light  and  heat.  A  bare  struggle  for  ani- 
mal existence  makes  up  nearly  all  of  life,  and  the  higher 
cravings  of  human  nature  are  unknown.  Only  a  single 
race,  the  Eskimo,  has  become  fitted  to  this  severe  en- 
vironment. 

311.  People  of  the  northern  deserts. — These  lands  stretch 
south  from  the  polar  seas,  and  are  covered  with  snow  most 
of  the  year.      The 

soil  is  always  deeply  -^^_ 

frozen  except  a  few 

inches  at  the  surface  -^^~ 

in  the  short  sum-  ^ 
mer.  Such  regions 
are  found  in  Alaska, 
British  America,and 
Siberia.  In  the  sum- 
mer many  herbs  and 
a  few  stunted  wood- 
ed plants  put  forth 
leaves  and  blossoms. 
Mosses  abound,  on  which  the  reindeer  feed.  The  people 
can  not  live  in  villages  or  settled  homes,  for  they  must 
move  to  get  food.  They  can  not  till  the  soil,  for  crops 
will  not  ripen.  A  few  leaves  and  berries  are  the  only 
plant  food.  Fish  and  the  milk  and  flesh  of  reindeer  are 
their  chief  dependence,  and  the  fish  must  be  diligently 
sought  and  dried  during  the  short  summer.  Life  is  in 
tents,  often  moved,  and  is  nearly  as  barren  as  that  of  the 
Eskimo. 

312.  Temperate  forests  of  North  America.— Here  lived 
Indians.      They  were  hunters  and  fishers,  but  depended 


Fig.  257. 


-Life  on  the  Siberian  plain.    A  Samoyed 
sled  drawn  by  reindeer. 


362    AN  INTRODUCTION   TO   PHYSICAL  GEOGRAPHY 


largely  on  seeds  and  fruits  of  wild  plants,  and  many  tribes 
had  the  beginnings  of  agriculture.  Some,  as  the  JPueblos 
of  the  southwest,  lived  in  permanent  villages,  with  well- 
built  houses  of  stone; 
others  were  more  or  less 
migratory,  "making  tem- 
porary shelters  of  boughs 
and  bark,  or  portable 
tents  of  skins.  They 
were  expert  in  basketry 
and  pottery,  but  knew 
nothing  of  iron,  and  had 
trained  no  animal  to 
their  service.  They  dwelt 
in  a  land  which  was 
able  to  nourish  a  far 
liigher  society,  and  upon 
which,  during  a  short  oc- 
cupation by  a  more  ad- 
vanced race,  the  highest 
type  of  human  life  has 
established  itself.  Such 
a  forest  region  gives  us 
at  first  the  savage,  next 
the  trapper,  then  the 
[)ioneer  farmer,  labori- 
ously clearing  the  trees 
from  a  few  acres  to  make 
space  for  field  and  or- 
chard. Gradually  the 
forests  melt  away,  roads 
are  built,  cities  grow, 
and  all  the  signs  of  com- 
plex civilization  appear. 
313.  Tropical  lands. — Xo  single  description  will  suffice 
for  man's  use  of  the  earth  in  warm  countries.     In  general 


Fig.  258.— Indian  basketry.  This  Indian  wom- 
an of  Utah,  clad  in  buckskin,  has  a  car- 
rying basket,  a  basket  for  winnowing 
seeds,  and  a  basketry  cap. 


'THE  EARTH  AND  MAN 


363 


we  may  say  that  continued  heat  makes  man  less  active  and 
keen  than  in  the  temperate  lands,  and  more  disposed  to  a 
sluggish  reliance  on  the  gifts  of  nature.  These  in  turn  are 
often  abundant,  nuts  and  fruits  growing  freely,  and  nour- 
ishing man  without  effort  on  his  part.  At  the  same  time 
the  warmth  enables  life  to  go  on  without  much  shelter  or 
clothing.  Hence  there  is  little  incentive  to  endeavor,  and 
the  tropical  races,  as  a 
rule,  do  not  use  the  earth 
wisely,  or  make  progress 
in  the  higher  arts  and  oc- 
cupations. 

In  hot  deserts,  as  the 
Sahara,  conditions  are 
quite  different.  Life  there 
requires  activity  and  strug- 
gle. Oases  —  rare  spots 
where  abundant  water 
makes  the  soil  fertile — 
are  planted  with  date- 
palms,  and  yield  much  food.  But  the  broad  face  of  the 
land  bears  so  scanty  a  growth  of  grasses  and  herbs  that  it 
can  give  support  only  to  herds  which  continually  move 
from  place  to  place.  So  life  is  chiefly  pastoral  and  migra- 
tory. It  is  also  in  part  commercial,  because  the  desert,  like 
the  ocean,  is  a  barrier  which  must  be  crossed  to  exchange 
the  products  of  richer  lands  on  either  side. 

314.  Man  in  temperate  climates. — Let  us  think  of  such  a 
region  as  the  United  States  or  central  Europe.  By  reason- 
able toil  abundant  food  can  be  drawn  from  the  soil,  hence 
the  wandering  life  of  the  hot  and  cold  deserts  is  unneces- 
sary. Man  has  time  to  make  a  home  and  to  gather  about 
him  its  conveniences  and  refinements.  The  struggle  to 
live  is  not  so  severe  as  to  make  his  life  barren,  but  enough 
effort  is  needed  to  keep  him  in  the  ways  of  strength  and 
growth.     If  he  till  the  soil,  he  must  be  diligent  in  summer, 


Fig.    259.— Indian    pottery.       A  water  jar 
made  in  the  Pueblo  of  Zniii,  New  Mexico. 


364   AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


to  provide  food  and  other  supplies  for  winter.  If  he  do 
not  cultivate  the  earth,  he  must  husy  himself  with  products 
which  he  can  exchange  for  food  and  his  other  necessities. 
In  temperate  latitudes  more  than  elsewhere,  civilization 
has  developed  division  of  labor.  Primitive  or  savage  men 
have  few  needs,  and  each  one  must  meet  them  all.  Civilized 
men  have  many  needs,  and  they  satisfy  them  by  working 
for  one  another,  and  exchanging  the  work  of  their  hands. 


Fig.  260.— The  commerce  of  Sahara  is  by  means  of  caravans— long  lines  of  laden 

camels. 

The  cold  and  poverty  of  the  north,  the  heat  and  plenty  of 
the  tropics,  do  not  blight  human  life  in  the  countries  that 
lie  between.  Temperate  climates  have  produced  the  in- 
quiring, daring  men,  who  have  sought  out  the  unknown 
parts  of  the  earth,  and  set  going  the  machinery  of  com- 
merce everywhere. 

We  learn  in  our  study  of  history  of  great  migrations  of 
tribes  from  Asia  westward  into  Europe,  and  southward  and 
westward  in  Europe  to  the  Mediterranean  and  the  Atlantic. 
Early  English  history  is  the  story  of  the  Roman,  the  Ger- 
man, the  Dane,  and  the  Xorman  pushing  into  the  British 
Islands.  The  settlement  of  America  is  the  further  move- 
ment of  these  great  human  waves  to  the  westward.  Thus 
man  illustrates  the  law  described  in  Section  296  as  the  tend- 


THE  EARTH  AND  MAN  365 

ency  to  spread.  He,  of  course,  moves  with  more  or  less 
conscious  purpose.  The  love  of  adventure  and  desire  to 
know  new  lands  make  a  part  of  his  reason  for  moving,  but 
in  general  man  migrates  to  find  fertile  lands  or  to  escape 
oppression. 

315.  The  influence  of  the  sea. — The  oceans  are  the  high- 
way of  nations.  The  classic  peoples  navigated  the  Medi- 
terranean. Gradually  they  crept  beyond  the  Pillars  of 
Hercules  (Straits  of  Gibraltar),  and  coasted  along  the 
shores  of  Africa  and  Europe.  Then  the  Korse  mariners 
threaded  the  northern  seas,  and  finally  the  great  modern 
voyages  began,  which  ended  in  the  knowledge  of  all  waters. 
To  meet  the  dangers  of  the  ocean,  challenge  its  mystery, 
and  compel  it  to  give  up  its  secrets,  has  educated  and 
splendidly  developed  civilized  man.  The  great  nations  of 
the  world  have  usually  been  found  on  the  sea-border.  Ro- 
man, Greek,  Northman,  Englishman,  Dutchman,  and  Span- 
iard— all  have  illustrated  this  principle.  The  Roman  Em- 
pire was  gathered  around  the  Mediterranean.  Britain  is  a 
great  empire  because  her  sons  have  crossed  the  seas.  Cities 
grow  up  along  shore-lines  and  become  centers  of  commerce 
and  travel.  Their  life  is  broader  and  more  various  in  its 
occupations  and  interests  than  the  life  of  inland  places. 
Fishing  determines  the  life  of  many  coastwise  towns,  and 
in  these  modern  days  the  ocean-border  becomes  a  summer 
camp,  where  crowded  dwellers  of  the  city  and  inland  people 
may  seek  rest,  and  enjoy  in  body  and  mind  the  peculiar  in- 
fluences of  the  sea. 

316.  Life  among  mountains. — It  is  not  easy  to  describe 
all  the  effects  of  mountain  life,  or  to  tell  how  mountain 
people  differ  from  those  of  the  sea.  But  one  fact  is  plain, 
and  is  perhaps  the  chief  one.  Mountain  people  live,  as  a 
rule,  in  narrow  valleys,  and  are  much  secluded  from  one 
another  and  from  dwellers  on  the  plains.  This,  of  course, 
does  not  apply  to  the  mountains  of  western  North  America, 
where  metallic  deposits  have  attracted  the  most  active  men, 


366    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

and  where  roads  and  telegraphs  foster  travel  and  constant 
interchange  of  thoughts  and  things. 

But  we  can  find  shut-off  people  among  the  southern  Ap- 
palachians, in  western  Xorth  Carolina,  eastern  Kentucky, 
and  Tennessee.  There  the  forests  remain.  Until  lately, 
no  railways  had  entered  the  region.  Visitors  from  the  out- 
side world  were  few.  Ancient  ways  are  the  rule,  and  there 
has  hardly  been  progress  since  white  people  first  settled  in 
those  regions.  Indeed,  instead  of  progress  there  has  been 
a  falling  back  into  coarse  and  ignorant  ways.  The  peasant 
life  of  Switzerland — that  is,  of  the  Alpine  part  of  that 
country — shows  what  we  mean.  These  people  are  thrifty, 
simple-hearted,  and  know  little  of  the  outside  world.  Their 
solitary  life,  however,  is  more  and  more  invaded  and 
changed  as  multitudes  of  people  seek  the  mountains  as  a 
playground. 

317.  Geography  and  history  of  North  America. — The  dis- 
coverers of  our  continent  came  over  the  sea  from  the  East. 
Hence  they  landed  on  eastern  shores,  and  sailed  into  the 
bays  and  rivers  that  there  join  the  ocean.  The  Spanish  dis- 
coverers occupied  the  West  Indies  and  the  shores  of  the 
Gulf,  and  carried  exploration,  conquest,  and  settlement 
across  the  plateaus  and  mountains  of  present  Mexico,  Kew 
Mexico,  Arizona,  and  California,  to  the  shores  of  the  Pa- 
cific. The  French  devoted  themselves  to  the  gulfs,  islands, 
peninsulas,  and  rivers  of  the  St.  Lawrence  region,  made 
long  voyages  on  the  Great  Lakes,  and  toiled  along  the 
streams  and  across  the  prairies  of  the  Mississippi  Valley. 
The  English  sought  all  shores,  but  settled  by  the  harbors 
of  the  Atlantic  from  the  Carolinas  to  New  England.  Win- 
ning New  York  from  the  Dutch,  and  at  length  wresting 
the  St.  Lawrence,  Canada,  and  the  West  from  the  French, 
they  made  the  Anglo-Saxon  people  the  future  masters  of 
North  America.  The  destinies  of  the  continent  were  de- 
cided in  the  temperate  region. 

The  early  English   settlements  formed  a  chain  along 


THE  EARTH  AND  MAN 


367 


the  Atlantic  coast.  New  England  had  abundant  harbors, 
about  which  grew  Salem,  Plymouth  and  Boston  in  Massa- 
chusetts; and  Providence  and  Newport  in  Khode  Island. 
Then  the  open,  fertile  Connecticut  Valley  invited  settle- 
ment. 

New  York  is  the  natural  gate  of  the  eastern  United 
States.  Its  harbor,  the 
tidal  Hudson,  provides 
for  the  ships  of  all  seas, 
and  the  low  pass  of  the 
Mohawk  Valley  makes 
easy  the  transfer  of 
men  and  products  be- 
tween the  ocean  and 
the  great  inland  States 
of  the  Mississippi  and 
Lake  regions.  But  for 
Niagara  Falls  and  the 
rapids  of  the  St.  Law- 
rence, the  metropolis 
of  America  might  have 
been  on  the  Gulf  of  St. 
Lawrence.  Philadel- 
phia developed  in  colo- 
nial times  upon  the 
estuary  of  the  Dela- 
ware. Another  group 
of  the  earliest  settle- 
ments was  made  along 
the  shores  and  rivers 
of  the  Chesapeake,  in  Virginia,  and  later  in  Maryland.  The 
country  is  flat,  and  divided  by  tidal  rivers.  "Into  the 
depths  of  the  shaggy  woodland,  for  many  miles  on  either 
side  of  the  great  bay,  the  salt  tide  ebbs  and  flows.  One 
can  go  surprisingly  far  inland  on  seagoing  craft,  while  with 
a  boat  there  are  but  few  plantations  on  the  old  York  penin- 
25 


Pig.  261.— The  mission  church  at  San  Luis 
Key,  Cal.,  a  record  of  early  Spanish  set- 
tlement. 


368   AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

sula  to  which  one  can  not  approach  very  near"  (John 
Fiske).  Thus  plantations  were  much  by  themselves,  roads 
were  few,  and  there  was  little  life  in  towns. 

As  the  narrow  belt  along  the  sea  became  occupied,  fron- 
tiersmen pushed  their  way  through  the  forests,  along  the 


Fig.  262. 


-The  pass  of  the  Mohawk,  used  by  exploration,  early  migration,  canal 
traffic,  and  now  by  still  greater  rail  traffic. 


valleys  and  over  the  ridges  of  the  Appalachian  Mountains 
into  the  fertile  plains  of  Kentucky,  Ohio,  and  the  West. 
For  a  long  time  this  mountain  wall  held  the  colonies  to- 
gether, until  they  became  strong,  separated  themselves 
from  the  mother  country,  pushed  over  the  low,  wooded 
mountains,  and  covered,  within  two  or  three  short  genera- 
tions, the  smooth  and  open  grounds  of  the  Mississippi 
basin.  The  tide  of  Anglo-Saxon  settlement  was  for  two 
centuries  held  in  by  mountains  near  the  shore-line,  and 
then  swept  to  the  base  of  the  Rocky  Mountains  in  much 
less  than  half  that  period.  This,  in  part  at  least,  is  due  to 
the  smoothness  of  the  interior  country,  the  richness  of  its 
soil,  and  its  comparative  freedom  from  forests.     The  two 


THE  EARTH  AND  MAN 


369 


natural  features  which  have  shaped  the  modern  life  and 
industries  of  the  western  mountains  and  plateaus  are  the 
dryness  of  the  climate  and  the  wealth  of  precious  metals. 
The  Pacific  coast  region  is  feeling  new  conditions  in  its 
growing  relations  to  the  lands  across  the  Pacific,  and  the 
ports  of  the  West  may,  in  years  to  come,  vie  with  those  of 
the  Atlantic  seaboard.  Meantime  the  trafiic  of  the  Great 
Lakes  resembles  in  importance  that  of  an  ocean,  and  the 
tonnage  of  Chicago,  Cleveland,  or  Buffalo  compares  with 
that  of  Liverpool  or  Hamburg. 


Fig.  263.— Shipping  in  the  harbor  of  New  York.    The  bridge  joining  Manhattan  and 
Brooklyn  is  so  high  in  the  middle  that  ships  pass  under. 


318.  Summary. — In  different  parts  of  the  world  the  sev- 
eral races  of  men  have  in  ages  past  developed.  The  white 
man,  the  yellow,  red,  and  black  man  are  what  they  are, 
largely  through  the  influence  of  their  surroundings,  gain- 
ing their  appearance  and  habits  through  generations.  As 
mankind  in  past  times  has  thus  split  into  branches,  using 


370   AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 

many  languages,  so  now  modern  commerce  and  knowledge 
tend  to  bind  the  world  together.  In  ancient  and  in  modern 
days,  from  motives  of  war,  religion,  science,  and  trade,  man 
has  sought  a  knowledge  of  the  world,  and  helped  to  build 
up  the  science  which  we  now  study — Geography.  As  the 
earth  has  had  its  influence  on  man,  so  man  has  stamped 
the  earth  everywhere  with  his  presence.  He  has  fast  driven 
out  the  wild  animals,  or  trained  them  to  his  use.  He  has 
swept  the  native  plants  from  the  fields  and  filled  them  with 
improved  fruits  and  grains.  He  has  sailed  upon  the  waters 
and  made  a  network  of  roads  upon  the  land.  He  is  con- 
stantly learning  new  uses  for  mineral  substances,  and  is 
pouring  out  water  on  the  deserts  to  make  them  fruitful. 
He  predicts  storms  and  floods.  He  uses  the  forces  of 
nature  to  turn  the  wheels  of  factories,  to  bring  what  he 
wishes  from  all  lands,  and  to  flash  his  thoughts  around  the 
world.  Dependent  on  the  earth,  he  subdues  the  earth  to 
his  use. 


3/Ty 


INDEX 


Adirondacks,  forms,  139, 179, 180 ;  eli 

mate,  191 ;  uses,  192 ;  forestry,  323 ;  ^ 

deer,  331. 
Africa,  railway,  358.    (See  also  Egypt, 

Sahara.) 
Agassiz,  Lake,  156. 
Air  and  life,  334. 
Air,  composition  of,  223. 
Alabama,  waterfall,  39;  mountains,  179. 
Alaska,  Yukon  Kiver,  72 ;  glaciers,  126, 

131,  133,  137,  138;  plains,  165,  166; 

volcanoes,  210 ;  coast,  307 ;  marine 

terraces,  314 ;  forests,  321 ;  dug-out, 

318. 
Alleghany  plateau,  182. 
Alluvial  cone  lakes,  60. 
Alluvial  cones,  43. 
Alpine  plants,  324. 

Alps,  glaciers  of,  119-124,  357;  struc- 
ture and  scenery,  185;  climate,  190; 

inhabitants,  191,  360;  as  a  barrier, 

193. 
Altitude  and  temperature,  245;  and 

life,  332. 
Andes,  187,  193. 
Anemometer,  257,  258. 
Animals,  wasting  of  rocks  by,  83 ;  in 

caverns,   100;    of   North    America, 

328-331 ;  as  food,  349. 
Antarctic  ice-sheet,  131. 
Antelope,  330. 
Ant-hill,  83. 
Anticyclones,  259,  271. 
Antitrades,  267. 


Appalachian  forests,  320. 

Appalachian  Mountains,  rounded  sum- 
mits, 92;  structure,  179 ;  climate,  190; 
inhabitants,  366  ;  as  a  barrier,  368. 

Appalachian  valleys,  64. 

Arctic  region,  animals,  328 ;  conditions 
of  human  life,  861. 

Arid  region,  232;  vegetation,  326,  327. 

Arizona,  plateau,  174;  Mount  San 
Francisco,  208  ;  arid  vegetation,  326. 

Arkansas  River,  49,  67. 

Artesian  wells,  103. 

Ashes,  volcanic,  200,  219. 

Asia,  drifting  sands,  112 ;  glaciers,  124 ; 
mountains,  187  ;  rainfall.  234. 

Atlantic  coast,  302-307;  fall  line  and 
drowned  valleys,  65 ;  dunes,  114. 

Atlantic  Coastal  Plain,  151. 

Atlantic  Ocean,  winds,  261 ;  depths, 
280 ;  currents,  294. 

Atmosphere,  12,  223-273;  an  agent  ot 
rock-wasting,  78 ;  weight  and  height, 
225 ;  temperature,  238-252  :  pressure, 
253-256  :  general  circulation,  266. 

Atoll,  284,  285. 

Australia,  rainfall  of,  235. 

Avalanches,  85,  86. 

Axis,  inclination  of,  20. 

Bad  lands,  91,  92,  93. 
Barometer,  253. 
Barrier  beaches,  306,  310. 
Barrier  reefs,  284. 
Barriers  and  passes,  193. 

371 


372    AN  INTRODUCTION  TO   PHYSICAL  GEOGRAPHY 


Barriers  to  migration,  341. 

Basketry,  362. 

Bayous,  55. 

Beaches,  303,  305,  306,  309,  310,  313. 

Beaver,  329. 

Beaver  dams,  83,  334. 

Bonneville,  Lake,  158,  159,  314. 

Book  of  the  Dead,  360. 

Bore,  tidal,  291. 

Boulder  clay,  133. 

Bow  and  arrow,  349,  350. 

Brook,  a  carrier,  8. 

Buffaloes,  330. 

Butte,  91,  93. 

Cables,  telegraphic,  301. 

Calabrian  earthquakes,  220. 

Calcium  carbonate,  76,  99. 

California,  drainage  system,  71 ;  soils, 
87 ;  gold,  97 ;  dust  storms.  111 ; 
glaciers,  126 ;  U-trough,  140 ;  pot- 
holes, 141 ;  glacial  lakes,  142 ;  cen- 
,  tral  valley,  161,  178 ;  Great  Basm, 
175 ;  Sierra  Nevada,  176 ;  mountain 
barrier,  193;  volcanoes,  206;  rain- 
fall, 232 ;  climates,  270 ;  coast,  307  ; 
Golden  Gate,  307,  316;  plant  zones, 
320 ;  forestry,  323 ;  yucca,  327 ;  sea- 
lions,  343 ;  oil  wells,  355 ;  mission 
church,  367. 

Canada,  glaciers,  126 ;  glacial  lakes, 
141, 143 ;  ice-sheet,  144;  lake  plains, 
155 ;  plains,  165 ;  temperature  at 
Montreal,  244 ;  forests,  321 ;  ani- 
mals, 328. 

Canyon,  28. 

Cape  Cod,  map,  15;  dunes,  114,  115, 
116 ;  coast  features,  304 ;  harbor,  316. 

Caribou,  329. 

Cascade;.  Mountains,  207;  glacier,  125. 

Cascades,  37,  38. 

Cascades  of  the  Columbia,  108. 

Catskill  plateau,  182;  map,  14;  shift- 
ing of  divide,  66;  due  to  wast- 
ing, 87. 

Caverns,  98. 

Central  American  volcanoes,  210. 


Charleston  earthquake,  221. 

Chattanooga,  184. 

Chelan  River  delta,  54. 

Chesapeake  Bay,  a  drowned  river  val- 
ley, 64,  153;  map,  65;  shores,  152; 
tidal  rivers,  307,  367. 

China,  loess  of,  113. 

Cincinnati,  temperature  curve,  244. 

Cirrus  clouds,  229,  230. 

Cities  and  harbors,  315. 

Cleopatra's  Needle,  79,  8L 

Cleopatra  Spring,  101. 

Climate,  270-273  ;  of  mountains,  189  , 
and  life,  337;  in  relation  to  man, 
363,  364. 

Clothing,  350. 

Clouds,  228;  in  relation  to  radiation, 
240. 

Coal,  under  prairies,  l63 ;  of  Alle- 
ghany Plateau,  183;  of  Colorado, 
188;  as  fuel,  353. 

Coasts,  302-318. 

Colorado,  Arkansas  Valley,  67 ;  gold, 
97  ;  hogback,  89  ;  Glenwood  Springs, 
101;  landslides,  107;  glaciers,  124; 
Kocky  Mountains,  168;  parks,  172; 
plateaus,  174 ;  mineral  deposits,  188; 
passes,  193;  lava  sheets,  216;  plant 
groups,  325 ;  cog  railway,  357. 

Colorado  canyon,  frontispiece^  71,  90. 

Colorado  plateaus,  174. 

Colorado  Kiver,  70;  rapids,  38;  delta, 
56. 

Colors  of  the  ocean,  287 ;  of  the  sky, 
237. 

Columbia  Kiver,  72;  landslides,  108; 
dunes,  112. 

Columnar  structure,  215,  216. 

Commerce  of  the  Great  Lakes,  69, 

Communication  and  record,  358. 

Compass,  274. 

Conduction,  239. 

Connecticut,  soils,  87 ;  mountains,  181. 

Connecticut  Valley,  68,  70. 

Continental  glacier,  southern  bound- 
ary, 145. 

Continental  glaciers,  128, 132. 


INDEX 


373 


Continental  shelves,  280,  281. 

Contour  maps,  15. 

Coral  reefs,  283. 

Cordillera,  177. 

Corn,  348. 

Cotidal  lines,  293. 

Cotton,  351. 

Crabs,  344. 

Crater,  of  Vesuvius,  198 ;  Costa-Rican, 
211. 

Crater  Lake,  216,  217. 

Craters  of  Hawaii,  203;  of  West  In- 
dies, 209. 

Creep  of  soils,  84,  85. 

Crevasses,  120,  122. 

Crystalline  rocks,  6,  76. 

Cumberland  plateau,  183. 

Cumulus  clouds,  229,  230. 

Currents,  ocean,  294. 

Cut-off,  51. 

Cyclones,  paths  of,  260 ;  tropical,  265  ; 
of  the  westerly  winds,  268;  predic- 
tion of,  269 ;  of  the  United  States, 
271. 

Cypress  knees,  335,  336. 

Dana,  J.  D.,  212. 

Darwin,  Charles,  on  work  of  earth- 
worms, 84 ;  on  bumblebees  and  clo- 
ver, 342. 

Dawson,  George  M.,  329. 

Day  and  night,  20. 

Death  Valley,  175. 

Declination,  magnetic,  275. 

Deep-sea  deposit,  300. 

Deer,  330. 

Dekkan  Plateau,  216,  218. 

Delaware  Bay,  tides  in,  293  ;  early  set- 
tlement, 367. 

Delaware  coastal  plain,  151. 

Delaware  Water-Gap,  63. 

Deltas,  54,  61. 

Derelicts,  296. 

Desert  plants,  327. 

Deserts,  wind  work  on.  Ill ;  Sahara, 
112,  236;  Western  United  States, 
232. 


Dew  and  frost,  227. 

Dew-point.  228. 

Dip,  magnetic,  277. 

Distributaries,  55. 

Divides,  36  ;  shifting  of,  65. 

Doldrums,  260,  266,  267. 

Drainage,  development  of,  59  ;  imper- 
fect, 60  ;  controlled  by  rocks,  62 ;  of 
rising  and  sinking  lands,  63  ;  modi- 
fied by  ice-sheet,  149. 

Drift,  87,  132. 

Drowned  river  valleys,  64, 153. 

Drumlins,  137,  303. 

Dug-out,  356,  358. 

Dunes,  110 ;  restraint  of,  116. 

Dust,  transported  by  wind,  109  ;  in  the 
air,  225  ;  volcanic,  206,  237. 

Earth,  general  characters,  1-16;  crust, 
4 ;  in  relation  to  sun,  17-27  ;  mo- 
tions, 18;  magnetism,  274-278;  in 
relation  to  animals  and  plants,  319- 
345  ;  in  relation  to  man,  346-370. 

Earthquake  waves,  289. 

Earthquakes,  187, 198,  220-222. 

Egypt,  picture  writing,  360. 

England,  dunes,  115;  rainfall,  233, 
234  ;  coast,  310  ;  estuaries,  316. 

English  exploration,  366. 

English  sparrow,  338. 

Environment,  influence  on  plants  and 
animals,  337-343  ;  influence  on  man, 
359. 

Erratics,  133. 

Eskers,  136,  137. 

Eskimos,  361. 

Estes  Park,  172. 

Etna,  Mount,  201. 

Europe,  dunes,  115,  117 ;  glacial  pe- 
riod, 150 ;  mountains,  185,  192  ;  rain- 
fall, 233. 

Explosions,  volcanic,  218. 

Eye  of  the  storm,  266. 

Fall  Line,  65,  70,  153. 
Fingal's  Cave,  216,  310. 
Finger  Lakes,  143. 


374    AN  INTRODUCTION   TO  PHYSICAL  GEOGRAPHY 


Fiords,  303,  307. 

Fishing,  301. 

Fiske,  John,  368. 

Flax,  351. 

Flint  implements,  352,  353. 

Floe-ice,  131,  297. 

Flood-plains,  45. 

Floods,  47. 

Flora,  324. 

Florida,  springs,  100 ;  coastal  plain,  162. 

Fog,  228. 

Food,  animal,  349. 

Food,  plant,  346. 

Forestry,  322. 

Forests,  319. 

Forests,  temperate,  in  relation  to  man, 

361,362. 
Forms  of  land,  due  to  surface  wasting, 

87-94. 
France,  dunes,  115,  116. 
French  exploration,  366. 
Front  Range,  172. 

Frost,  227 ;  wasting  of  rocks  by,  81. 
Fuels,  353. 

Galveston,  307. 

Gas,  natural,  183,  354. 

Geikie,  A.,  116. 

Geography  and  history  of  North  Amer- 
ica, 366. 

Georgia,  coastal  plain,  152. 

Geysers,  102, 103. 

Giant  kettles,  141. 

Giant's  Causeway,  216. 

Gibbs  Canyon,  140. 

Gipsy  moth,  339. 

Glacial  lakes,  146,  156. 

Glacial  period,  10,  132-135,  143-150; 
in  relation  to  soils,  95 ;  cause  of  mi- 
gration, 340. 

Glacial  rounding,  138, 139. 

Glacial  scratches,  134. 

Glaciers,  119-150 ;  mountain,  119-128  ; 
continental,  128-135;  cause  of,  131; 
forms  of  land  made  by,  135-143;  of 
North  America,  124-130.  (See  also 
Glacial  period.) 


Golden  Gate,  307,  316. 

Gold-mines,  97, 188, 

Gorge,  character  and  origin,  28. 

Gorner  Glacier,  119. 

Gradient,  atmospheric,  257. 

Grand  Canyon  of  the  Colorado,  38,  71, 
90. 

Granite,  6,  76,  88. 

Gravitation,  292. 

Great  Basin,  175, 178. 

Great  Britain,  rainfall,  233,  234.  (See 
also  England  and  Scotland.) 

Great  Lakes,  in  relation  to  rivers,  69 ; 
dunes,  113;  origin  of  basins,  143; 
preceded  by  glacial  lakes,  146 ;  bor- 
dering plains,  156  ;  exploration,  366  ; 
commerce,  369. 

Great  Plains,  163;  treeless,  320, 
324. 

Great  Salt  Lake,  160. 

Great  Salt  Lake  Desert,  158. 

Greenland  ice-sheet,  128; 

Green  Mountains,  189. 

Ground-water,  103. 

Gulf  plains,  162,  320. 

Gulf  Stream,  294. 

Hachures,  15. 

Harbors  and  cities,  315. 

Hawaiian  volcanoes,  203. 

Heat,  239. 

Heat  equator,  250. 

Hemp,  351. 

Herculaneum,  200. 

Highlands  of  the  Hudson,  58. 

Highlands,  Scottish,  59,  185,  192. 

Himalaya  Mountains,  124,  187. 

History    and     geography    of    North 

America,  366. 
Hog-back,  89. 
Holland,     dunes,    ll5,    116;     dikes, 

314. 
Hood,  Mount,  208. 
Horse  latitudes,  260,  267. 
Hot  springs,  101. 
House  Range,  176,  177. 
Hudson    River,  route   of  exploration 


INDEX 


375 


and  commerce,  70,  315,  367;  tidal 
estuary,  304;  head  waters,  323. 

Hudson  Valley,  worn-down  plain,  14, 
161 ;  stage  of  development,  58. 

Humidity,  226. 

Hurricanes,  265,  307. 

Icebergs,  126, 130,  297. 

Ice-jam,  34. 

Iceland,  209. 

Ice-sheets,  128. 

Idaho,  Snake  Kiver  Canyon,  72 ;  lava 
sheets,  213. 

Igneous  rocks,  6,  76,  196. 

Illinois,  river  valley,  67;  artesian 
wells,  104;  prairie,  162. 

Illinois  River,  16,  67. 

India,  lava  sheets,  216;  soils,  218; 
rainfall,  235  ;  monsoons,  262,  263. 

Indiana,  dunes,  113 ;  prairie,  162. 

Indian  Ocean,  winds,  262,  263. 

Indians,  bow  and  arrow,  349,  350; 
stone  implements,  352,  353 ;  habita- 
tions, 354 ;  dug-out,  356,  358 ;  rock 
carving,  360;  basketry,  362;  pot- 
tery, 363. 

Iowa,  drift,  133;  prairie,  162. 

Irrigation,  163,  164,  271,  272. 

Island  life,  341. 

Islands,  coral,  283. 

Islands,  volcanic,  201,  203,  205,  209, 
283. 

Isobars,  254. 

Isogonics,  276. 

Isotherms,  246,  270;  for  January, 
248;  for  July,  249;  for  the  year, 
251. 

Italy,  climate,  189;  volcanoes,  196; 
earthquakes,  220. 

Japan,    earthquakes,     220;     rainfall, 

234. 
Joints,  28,  37,  38. 

Kames,  135. 

Kansas,  sink  hole,  98 ;  Great  Plains, 
164. 


Kentucky,  sink  holes,  60,  99 ;  soils,  87, 
96;  Mammoth  Cave,  98;  Cumber- 
land Plateau,  183 ;  mountain  life, 
366. 

Kilauea,  204. 

Kings  Chapel,  150. 

Krakatoa,  205,  211,  237,  290. 

Lagoons,  284,  285,  310. 

Lake  basins,  glacial,  141. 

Lake  deltas,  56. 

Lake  shores,  314;  dunes  on,  110-113. 

Lakes,  of  various  origins,  60 ;  glacial, 
146;  volcanic,  211,  216,  217. 

Land  and  sea  breezes,  262. 

Land  and  water,  7. 

Land  forms  due  to  surface  wasting, 
87-94. 

Landslides,  105-108. 

Land,  up  and  down  movements,  10. 

Latitude  and  life,  332. 

Latitude  and  longitude,  2. 

Latitude  and  temperature,  243. 

Lava  cascade,  205. 

Lava  sheets,  213. 

Lava  streams,  198,  203,  207. 

Life,  animal,  in  caverns,  100. 

Life  (plant  and  animal),  12,  319-345 ; 
in  relation  to  glacial  epoch,  150 ;  of 
mountain  lands,  365 ;  of  the  ocean, 
299,  343 ;  geographic  conditions  of, 
332-345. 

Life-saving  stations,  317. 

Light  and  color,  236-238. 

Light,  in  relation  to  life,  336 ;  source  of 
artificial,  354. 

Lighthouses,  317. 

Limestone,  76 ;  weathered,  79,  82. 

Llano  Estacado,  165. 

Loess,  113. 

Longitude,  2. 

Lookout  Mountain,  184. 

Los  Angeles,  oil  wells,  355. 

Louisiana,  soils,  87;  plain,  162;  tem- 
perature at  New  Orleans,  244;  har- 
bor, 316. 

Luray  Cavern,  99. 


376   AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


Magellan,  1,  298. 

Magnetism  of  earth,  274r-278. 

Maine,  drift,  136,  137  ;  coast,  302,  313  ; 
marine  terraces,  314 ;  life-saving  sta- 
tion, 317. 

Maize,  348. 

Malaspina  Glacier,  128, 133. 

Mammoth  Cave,  98. 

Man,  relations  to  the  earth,  346. 

Map  projection,  250. 

Maps,  kinds  of,  14. 

Mark  Twain,  52. 

Marthas  Vineyard,  moraine  and  wash 
plain,  138;  shores,  304,  310,  313. 

Martinique,  eruptions  on,  209. 

Maryland,  coastal  plain,  151 ;  early 
settlement,  367. 

Massachusetts,  water  power,  42,  149 ; 
Connecticut  Valley,  58,  70  ;  dunes, 
114,  116;  drumlins,  137;  wash 
plains,  138 ;  glacial  lakes,  141 ;  cli- 
mate, 191 ;  waterspout,  265  ;  fish- 
eries, 301 ;  coast,  303,  310,  313  ;  har- 
bors, 315,  316  ;  gipsy  moth,  339. 

Matterhorn,  185,  186. 

Meanders,  48,  49. 

Mediterranean  Sea,  volcanoes,  201. 

Mediterranean  seas,  280,  282. 

Meeting  of  the  land  and  sea,  302-318. 

Mercator  projection,  250. 

Meridians,  3. 

Meridians,  magnetic,  275. 

Mesa,  91. 

Mexico,  forests,  322 ;  animals,  331. 

Michigan,  dunes,  113. 

Michigan,  Lake,  312. 

Migration  of  animals  and  plants,  150, 
340. 

Migrations  of  men,  366-369. 

Mineral  springs,  100. 

Mineral  veins,  97, 188. 

Minnesota,  valleys,  67  :  glacial  lakes, 
141;  new  river  course,  149;  Ked 
Kiver  Valley,  156. 

Misery,  Mount,  210. 

Mississippi,  162. 

Mississippi  delta,  54. 


Mississippi    Kiver,    in    flood,  46,  48; 

meanders,  49,  51,  52. 
Mississippi  Kiver  system,  66.  • 
Mississippi   Valley,    162;    settlement, 

368. 
Missouri,  162. 
Missouri  Kiver,  67. 
Models,  topographic,  16. 
Mohawk  Valley,  stage  of  development, 

58 ;  as  a  gateway,  193,  315,  367. 
Monadnock,  Mount,  87. 
Monsoons,  262,  263. 
Montana,    avalanche    tracks,  85,   86; 

glaciers,  126;  vegetation,  190. 
Monte  Nuovo,  197. 
Montreal,  temperature-curve,  244. 
Moon  and  tides,  291. 
Moose,  329. 

Moraines,  120,  123, 125. 
Mosquito  Kange,  173. 
Mountains,  and  plateaus,  168-195  ;  due 

to  wasting,  87  ;  history,  182;  climate, 

189,  245  ;  influence  on  men,  191,365. 
Muir  Glacier,  126, 127. 
Musk-ox,  328. 

Nahant,  303,  304. 

Nansen,  130. 

Natural  gas,  183,  354. 

Navigation,  300. 

Nebraska,  Platte  Valley,  67 ;  Indian 

rock-carving,  360. 
Neck,  volcanic,  213. 
Needle,  magnetic,  274 ;  dip,  277. 
Nevada,  Great  Basin,  175 ;  rainfall,  232. 
New   England,  drainage  system,  70 ; 

drift,  133,  135;  mountains,  181 ;  for- 
ests, 323. 
Newfoundland,  313. 
Newfoundland,  Banks  of,  281,  296,  301. 
New  Jersey,  sinking  land,  63 ;  artesian 

wells,  104;    coastal  plain,  151,  153; 

lava  sheets,  214;  continental  shelf, 

282;  coast,  304,  313. 
New  Mexico,  plateaus,  174 ;  volcanoes, 

208  ;  Indian  pottery,  363. 
New  Orleans,  temperature-curve,  244. 


INDEX 


377 


New  York,  water  power,  42, 149 ;  val- 
leys, 58 ;  lakes,  61 ;  Sarajtoga  Springs, 
101;  drift,  132,  136,  137;  glacial 
scratches,  135  ;  pot-holes,  141 ;  gla- 
cial lakes,  141,  143, 156  ;  lake  plains, 
156,  157;  climate,  191;  coast,  304; 
lake  shore,  311,  312;  forestry,  323; 
prairies,  324 ;  early  history,  367.  (See 
also  Adirondack,  Catskill,  and  Mo- 
hawh  Valley.) 

New  York  Harbor,  315,  369. 

Niagara  Falls,  38-42,  61. 

Nile,  floods,  47,  48  ;  delta,  55. 

North  America,  rivers,  66-73 ;  glaciers, 
124;  plains,  161-167  ;  mountains  and 
plateaus,  168-185  ;  coasts  of,  302-308 ; 
plants  of,  319-328;  animals  of,  328- 
331 ;  relation  of  geography  to  his- 
tory, 366. 

North  Carolina,  dunes,  114;  coastal 
plain,  152;  placer  mining,  188 ; 
mountain  life,  366. 

North  Dakota,  Eed  Eiver  Valley,  156. 

Obsidian  Cliff,  215. 

Ocean,  279-301 ;  water,  286 ;  tempera- 
tures, 287  ;  waves,  288 ;  currents,  294 ; 
exploration,  298 ;  deposits  in,  299 ; 
life,  299,  343 ;  influence  on  mankind, 
365 :  ocean  basins,  279. 

Ohio,  temperatures  at  Cincinnati,  244. 

Oils  for  light,  354. 

Oil  wells,  355. 

Ontario  basin  and  Glacial  epoch,  147. 

Ontario,  Lake,  311,  312. 

Orbit  of  the  earth,  19. 

Oregon,  dunes,  112,  113;  volcanoes, 
207,  217. 

Ox- bow  lakes,  49,  51. 

Pacific  coast,  307 ;  commerce,  369. 

Pacific  Ocean,  281 ;  currents,  296. 

Palisades  of  the  Hudson,  214. 

Palmetto,  333. 

Parallels  of  latitude,  3. 

Park  Eange,  172. 

Parks  of  the  Rocky  Mountains,  171, 172. 


Passes,  193. 

Pass  of  the  Mohawk,  368. 

Peary,  K.  E.,  130. 

Peccaries,  331. 

Pelee  volcano,  209. 

Pene-plains,  161. 

Pennsylvania,  valleys,  58 ;  drainage 
system,  62;  large  spring,  100;  till, 
134 ;  changes  of  drainage,  149 ; 
mountains,  179,  183. 

Petroleum,  183,  354,  355. 

Physical  geography  defined,  13. 

Picture  language,  360. 

Piedmont  Plain,  161. 

Pikes  Peak,  170. 

Placer  mining,  188. 

Plains,  151-167  ;  marine,  151-155; 
lake,  155-160;  river,  160-161 ;  worn- 
down,  161 ;  of  North  America,  161- 
167. 

Plants,  wasting  of  rocks  by,  81 ;  of 
North  America,  319-328;  zones  of, 
320,  332 ;  as  food,  347. 

Plateau,  Alleghany,  182. 

Plateaus  and  mountains,  168-195. 

Plateaus,  Colorado,  174. 

Pliny,  200. 

Pompeii,  200. 

Potato,  348. 

Pot-holes,  37, 41, 141. 

Pottery,  363. 

Prairies,  162,  323. 

Precipitation,  231.  (See  also  Raiii- 
fall.) 

Pressure  of  the  atmosphere,  253-256. 

Prevailing  westerly  winds,  258,  267. 

Pueblos,  362. 

Puget  Sound,  307,  316. 

Pyrenees,  185,  193. 

Eadiation,  239. 

Railways,  356-358. 

Eain  and  snow,  230. 

Eainbow,  237. 

Rainfall,   231 :  of  Great  Britain,  233, 

234 ;  of  Australia,  235. 
Eainier,  Mount,  207. 


378    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


Eain  wash,  80. 

Kapids,  38,  44. 

Bedding  Spring,  159. 

Bed  River  Valley,  155. 

Relative  humidity,  227. 

Revolution  of  the  earth,  19. 

Rhode  Island,  soils,  87. 

Rhone  Glacier,  124,  357. 

Rhone  Valley,  141,  357. 

Rice,  348. 

River  basins,  36. 

River  plains,  160. 

Rivers,  28-73 ;  of  North  America,  66- 

73 ;  changed  by  ice-sheet,  149.    (See 

also  Streams.) 
River  terraces,  52. 
Rock-carvings,  360. 
Rock  ledges  and  waste  slopes,  89. 
Rocks,  5,  74  ;  kinds,  74 ;  wasting,  78 ; 

hardening,  97. 
Rocky  Mountains,  sharp   peaks,   93; 

lake  basin,  143;  in   Colorado,  168; 

climate,  190  ;  occupations,  191,  368  ; 

passes,  193  ;  plant  zones,  320. 
Rotation  of  the  earth,  18 ;  influence  on 

winds,  266. 
Run-off,  36. 
Russell,  I.  C,  208. 
Russian  thistle,  341. 

Sahara,  drifting  sands,  112;  dryness, 
236 ;  occupations,  363. 

St.  Clair  River  delta,  61. 

St.  Elias,  Mount,  128. 

St.  Lawrence  River,  49,  69. 

St.  Pierre,  destruction  of,  210. 

St.  Vincent  Island,  eruptions  on,  209. 

Sand  blast,  117. 

Sand,  carried  by  wind,  110. 

Sandstone,  74 ;  weathered,  78. 

Sandy  Hook,  305,  306,  311. 

San  Francisco,  Mount,  208. 

San  Juan  Mountains,  169. 

Santa  Maria  (caravel),  359. 

Sawatch  Range,  173. 

Scotland,  Highlands,  59,  185,192;  in- 
dustries, 192 ;  lava  sheets,  216;  rain- 


fall, 233,  234 ;  sea  cave,  310 ;  marine 

terraces,  314. 
Sea,  279-301.    (See  also  Ocean.) 
Sea-cliffs,  309. 
Sea-lions,  343. 
Seasons,  cause  of,  21-25. 
SenecJa  Lake  Valley,  58,  61, 140. 
Shale,  76 ;  broken  by  down-hill  creep, 

84. 
Shasta,  Mount,  206,  211. 
Sheets  of  lava,  213. 
Shelter,  352. 

Shelves,  continental,  280,  281. 
Shore-lines,    uplifted,  10;   of  glacial 

lakes,  146 ;  of  Lake  Bonneville,  158, 

160. 
Shore  of  Lake  Michigan,  106. 
Shores,  302-318 ;  wave  action  on,  289, 

309. 
Siberia,  154 ;  railway,  356 ;  native  life, 

361. 
Sierra  Nevada,  glacial  scenery,  142; 

uplift,  176 ;  map,  178 ;  forests,  321. 
Sink  holes,  60,  98. 
Sky,  colors  of,  237. 
Snake  River  Canyon,  72,  213. 
Sneffels,  Mount,  93. 
Snow,  231. 
Soils,    94-96;   local  and  transported, 

87 ;  glacial,  149 ;  in  relation  to  plants, 

336. 
Solution  of  rocks,  79,  81. 
Soufriere  crater,  209. 
South  America,  mountains,  187 ;  rain- 
fall, 233. 
South    Carolina,  coastal    plain,    152; 

earthquake,  221. 
South  Dakota,  bad  lands,  92 ;  artesian 

wells,  104;  Great  Plains,  165. 
South  Lookout  Peak,  169. 
South  Park,  172. 
Spanish  exploration,  366. 
Spits,  311,  312. 
Springs,  100. 

Stalactites  and  stalagmites,  99. 
Standard  time,  26. 
Stanley,  Dean,  112. 


INDEX 


379 


Steamship,  359. 

Stone  implements,  352,  353. 

Storms,  258,  259,  264-266;  cyclonic, 
258 ;  thunder,  264 ;  tropical,  265. 

Stratified  rocks,  5. 

Streams,  28-73 ;  work  of,  8 ;  relation 
to  gorge,  31 ;  source  of  water,  35 ;  de- 
velopment of  valley,  43 ;  relation  to 
rocks,  62. 

Stromboli,  201. 

Struggle  for  existence,  339. 

Sun  and  earth,  17-27. 

Surf,  289,  309. 

Susquehanna  River,  64. 

Swamps,  62,  314. 

Switzerland,  alluvial  cones,  43 ;  deltas, 
62  ;  avalanches,  85 ;  landslides,  107  ; 
glaciers,  119,  124,  131,  150;  glacial 
sculpture,  141  ;  glacial  lakes,  143 ; 
climate,  190;  industries,  191;  car- 
riage road,  357 ;  mountain  life,  366. 

Silvestri,  Monti,  202. 

Tahiti,  212. 

Talus,  29. 

Taylor,  Mount,  208. 

Tea,  349. 

Temperate  climates  in  relation  to  man, 
363. 

Temperature  of  the  atmosphere,  238- 
252 ;  measurement  of,  238  ;  of  night 
and  day,  241  ;  curves,  242,  244 ;  in 
relation  to  latitude,  243  ;  in  relation 
to  altitude,  245 ;  mapping,  246  ;  in 
relation  to  life,  332. 

Temperature  of  the  ocean,  287. 

Temple  Creek  Canyon,  29. 

Tennessee,  river  bends,  51 ;  moun- 
tains, 179, 183 ;  mountain  life,  366. 

Tepee,  354. 

Terraces,  52. 

Texas,  bad  lands,  91 ;  coastal  plain, 
162 ;  Llano  Estacado,  165  ;  coast,  307  ; 
animals,  331. 

Thermometer,  238. 

Thermometer  record,  242. 

Thunder-storms,  264. 


Tibet,  187. 

Tides,  290. 

Tidewater  Virginia,  151,  307,  367. 

Till,  133. 

Timber-line,  168,  320. 

Time,  standard,  26. 

Tobacco,  349. 

Tools,  352,  353. 

Tornadoes,  265. 

Trade-winds,  259. 

Travel,  modes  of,  356. 

Trellised  drainage,  63-65. 

Trinity  College,  82. 

Tropical  animals,  331. 

Tropical  lands    in    relation   to  man, 

362. 
Tundras,  of  Siberia,  155  ;  of  Alaska, 

165,  167;  animals,  328;  peoples,  361. 
Tuolumne  Monument,  139. 
Typhoons,  266. 

Underground  changes,  96-105. 

United  States,  drifting  sands.  111 ;  in 
the  Glacial  period,  132, 145  ;  weather 
maps,  247,  256,  258  ;  weather  predic- 
tions, 268  ;  climates,  270 ;  coasts,  302 ; 
Coast  Survey,  277, 299,  317  ;  Depart- 
ment of  Agriculture,  96,  116,  322; 
Hydrographic  Office,  296;  Weather 
Bureau,  48,  254,  268. 

Utah,  lake  plains,  158;  plateaus,  174 ; 
Great  Basin,  175 ;  old  shore-lines, 
314;  Indian  basketry,  362. 

U-troughs,  140,  141. 

Valley,  development  of,  43,  57. 

Veins,  97,  188. 

Vesuvius,  Mount,  196,  220. 

V -gorge,  31. 

Virginia,  Shenandoah  Valley,  58 ;  up- 
lands, 59  ;  soils,  96  ;  Luray  Cavern, 
99, 100  ;  Natural  Bridge,  99 ;  coastal 
plain,  151 ;  mountains,  179,  183 ; 
tidal  rivers,  307 ;  prairies,  324 ;  early 
settlement,  367. 

Vlies,  61, 148. 

Volcanic  cone,  history  of,  211. 


380    AN  INTRODUCTION  TO  PHYSICAL  GEOGRAPHY 


Volcanic  explosions,  218. 
Volcanic  lakes,  217. 
Volcanic  neck,  213. 
Volcanic  soil,  217. 
Volcanic  tuft",  219. 
Volcanoes,  196-222. 

Wasatch  Mountains,  175. 

Washington,  landslides,  108 ;  glaciers, 
125, 126 ;  volcanoes,  207  ;  lava  sheets, 
213;  rainfall,  232;  coast,  307;  har- 
bors, 316  ;  forests,  821. 

Wash  plain,  138. 

Waste,  in  stream  bed,  32;  local  and 
transported,  87. 

Waste  mantle,  4 ;  thickness,  85. 

Waste  slopes,  89. 

Water  and  land,  7. 

Water  and  life,  334. 

Waterfalls,  38. 

Water-gap,  63. 

Water-plants,  324. 

Water-power,  42,  149,  153. 

Waterspout,  265. 

Water  supply,  100-104. 

Water,  underground,  96. 

Water-vapor,  224,  227. 

Watkins  Glen,  58,  75. 


Waves,  288. 

Wave  work,  309. 

Weather  and  climate,  268-273. 

Weather  Bureau,  48,  254,  268. 

Weathering  and  soils,  74-108. 

Weather-maps,  247,  256,  258. 

Weather-signs,  269. 

Wells,  103. 

West  Indies,  volcanoes,  209 ;  hurri- 
canes, 266. 

Wheat,  347. 

Winds,  storms,  and  climate,  253-273. 

Winds,  cause  of,  256  ;  prevailing  west- 
erly, 258 ;  cyclonic,  258 ;  trade,  259, 
266 ;  of  the  Atlantic,  261 ;  terrestrial, 
266. 

Wind  work,  109-118. 

Winnipeg  Lake,  156. 

Wisconsin  drumlins,  137. 

Wyoming,  hot  springs,  101 ;  geysers. 
101, 103;  pass,  193.  (See  also  Yel- 
lowstone Park.) 

Yellowstone  Canyon,  30. 
Yellowstone  Park,  101-103,  215. 
Yukon  Kiver,  72 ;  delta,  56. 

Zones  explained,  21-25. 


(4) 


THE  END 


LE   CONTE'S   GEOLOGY. 


A  New  Revised  Edition.      New  Data.      Latest  Facts 

Elements  of  Geology 

A  Text-Book  for  Colleges  and  for  the  General  Reader 

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Hanover,  N.  H. 

"  Most  interesting.  Decidedly  the  most  practical  book  that  I 
have  seen  for  use  in  high  schools." — Miss  S.  A.  Edwards,  Philadelphia 
High  School  for  Girls. 

I  consider  it  the  best  written  and  best  illustrated  book  I  have  ever 
seen  for  secondary  schools." — C.  F.  Warner,  Mechanics  Arts  High 
School,  Springfield,  Mass. 

*'  The  most  attractive  text-book  of  Geology  for  secondary  schools 
that  I  have  seen.  The  illustrations  are  a  delight." — Belle  Shennan, 
Ithaca  High  School,  Ithaca,  N.   Y. 

*'  It  is  magnificent.  I  consider  it  superior  to  any  other  book  of  the 
kind  in  illustrations,  text,  and  adaptation  to  field  work." — Mrs.  L.  L. 
W.  Wilson,  Philadelphia  Normal  School. 

"  In  every  way  fully  equal  to  any  of  the  splendid  series  of  Twen- 
tieth Century  Text-Books.  Many  of  the  illustrations  are  new  and 
their  execution  is  perfect." — R.  I.  Schiedt,  Professor  of  Geology 
Franklin  atid  Marshall  College,  Lancaster,  Pa. 


D.     APPLETON    AND     COMPANY,     NEW     YORK, 


UNIVEESITY  OF  CALIFORNIA  LIBRARY, 
BERKELEY 

THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 

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demand  may  be  renewed  if  application  is  made  before 
expiration  of  loan  period. 


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